View Full Version : Mad idea or not ???
I'm looking into how I can get more grunt out of the GTA on my very limited budget :(
I want to keep the PRV ..Peugeot Renault Volvo ....V6 .
I was looking at a A610 3l turbo lump but they are few and far between ,£4k new from Ren and the last one on Ebay went for almost as much :sad2:
A Safrane or Laguna NA 3l is a possibility but there are a fair few issues in Turbo charging them ,9.1 compression ,inlet manifolds ,valves cams etc .etc ....
Some of the PRV engines are oddfire so they are out of the running .
Now then .....All the PRV cranks are the same main journals .The GTA turbo Z7U has a bore of 91 and a 63 stroke .The Espace/25 2.8 NA even fires are 91 and 73 .
Can I stroke it please :scratch: 2.8l turbo ???
I have loads of GTA pistons and liners ,2 full sets newly ringed .I can design and get manufactured a few things with my contacts in the toolmaking trade at mates rates or even work it off .
I was thinking about making some custom rods out of Aluminium ...
I can get the high spec Aero stuff ,3D cad it up and get it machined etc but will need a bit of guidance with the main design concept .The block may need some cut-outs to miss the new rods .I'm going to measure and CAD up a local area to model it all up ...
Found these guys on the web ...as usual the Aussies are the ali experts ??
http://motorsport.bdg.com.au/conrod.html
Basic idea sound ? Or the ramblings of 'a little knowledge .................
Andrew Cooke
03-12-2008, 17:58
I wouldn't bother with aluminium rods, they end up bulky.
Would that overly be an issue ?Are we talking bulky as a weight issue or need bulk for strength and they wont fit ? I could get them done in steel but the machining time trebles .
But the basic idea ? Is it a feasible route to go down ?
http://www.rrconnectingrods.com/aluminumrods.htm
a guy called colin massarani from round my neck of the woods built a 2.8L (or was it 2.9L ?) V6 turbo for his DIY Turbo 2 replica. He's a member, search for massarani, he doesn't come online too often. He used a crank from 'X' and pistons from 'Y'.... I don't remember the details. He'd tell you what you need to know :)
a guy called colin massarani from round my neck of the woods built a 2.8L (or was it 2.9L ?) V6 turbo for his DIY Turbo 2 replica. He's a member, search for massarani, he doesn't come online too often. He used a crank from 'X' and pistons from 'Y'.... I don't remember the details. He'd tell you what you need to know :)
i remember that guy from the old site, he never did post up any "detailed" pictures of his car though :dearme:
He's not in the Ms on here ....
What would be the major fundamental issues in doing something like that though ? Clearance ,balance ,compression ....No replacement for ...............:agree::disagree::laugh:
It would seem on face value a very tempting route given the lack of tuning knowledge and expense involved in the PRV world .Many do spout pearls of wisdom but no one knows anyone that's actually done it .Everything is bespoke in my little world :sad:
he didn't really do much with the website but he knew a thing or 2 about renaults :)
He had a couple of awesome cars. Didn't he also get hold of a Safrane Bi-Turbo? :worship: I'm sure he did get round to putting pics on the site (though not of his 5).
He had a couple of awesome cars. Didn't he also get hold of a Safrane Bi-Turbo? :worship: I'm sure he did get round to putting pics on the site (though not of his 5).
i think i remember this too! if im not mistaken it was a dark grey/tungyish colour and he actually bought the car from france..?
Taken from Wiki: In 1994, Renault (http://en.wikipedia.org/wiki/Renault) launched the high-performance 'Biturbo' version available in RXE and baccara finition. This model featured a twin-turbo, 262 hp (195 kW) evolution of the 3.0-liter V6 of alpine A610, developed with the assistance of German tuning (http://en.wikipedia.org/wiki/Tuning) firms Hartge (http://en.wikipedia.org/wiki/Hartge) and Irmscher, coupled with all wheel drive (http://en.wikipedia.org/wiki/All_wheel_drive). However, it was only available with a manual transmission, as no automatic gearbox existed anywhere in the world for a transversely mounted engine of that horsepower with AWD (http://en.wikipedia.org/wiki/All_wheel_drive). Given that automatic transmissions and V8 (http://en.wikipedia.org/wiki/V8) engines are strongly preferred in the price class where Biturbo competed, it is not surprising that less than 1000 Biturbos were sold.Production ended in September 1996.
Long Cours
In the same year, the French coachbuilder (http://en.wikipedia.org/wiki/Coachbuilder) Heuliez (http://en.wikipedia.org/wiki/Heuliez) presented the Long Cours, which was something like a station wagon (http://en.wikipedia.org/wiki/Station_wagon) version of the Safrane Biturbo in luxury Baccara trim.
Funny, as I was going to say, would it be possible to put an engine from one of these into the back of a GTA!
I'm off to look for pics of the Long Cours :D
http://www.carstyling.ru/resources/studio/94heuliez_renault_long_cours.jpg
Not much of a looker. :dearme:
New poster! (less than 10 posts)
Not a mad idea at all. I am with Mr Cooke though, ally rods aren't really a good idea. The links given both allude to their problems. They have a short fatigue life (fine for a drag motor doing a couple of runs at most between rebuilds), they are terrible for galling on the big-end shuts and they spin bearings.
My experience with these engines goes back to '96 and a twin turbo 3l GTA I helped build (that had Mitsubishi turbos, used a modified Volvo inlet manifold and a pair of enormous charge coolers but I left there before it was finished so never found out how it went) and unfortunately is all a bit hazy:scratch:, but I'm presuming the difference between the odd and even fire engines is the offset big-end journals? wouldn't it be easier to get an NA 3l lump, rebuild it with machined pistons for lower CR and use a different management system?
Otherwise just get stuck in, if you can get bits like rods made then anything is possible...
Safrane Bi-turbos are rarer than a610 and more expensive .I know that the last two crated units went for a lot of dosh .One was complete with turbos,loom ,even gearbox .It's in Ireland being plonked in a GTA .The other short motor is in an underground car park in that there London ...............They were the last two in existence I believe ....
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Now twin turbo is another route I'm looking into ;) If you look on the bench you can see the Volvo plenum you mention .This route requires custome xhaust mani ,coolers ,throttle etc X2 of course .But I paid £25 for the Volvo plenum ,it needs injector ports putting in but it's been done before .......All this was pulled off a body kitted GTA just recently ,it never ran ......
613614
If you can rack your brain Jim for any vague memories of what PRV bits you used I'd be very grateful :agree:
The 2.8NA oddfire ,yes offset journals .I think my Adaptronic will run the oddfire .That's another option ,with turbo heads 'cause of the sodium cooled valves and a set of custom pistons 9.5:1 on the 2.8 ...8.6:1 on the 2.5 turbo .
What compression could I get away with say a bar of boost ?
The turbo is 8.6:1 the 2.8 is 9.5:1 .The turbo piston top finishes flush with the liner top ,but it has a 70mm x 3.8mil high dome that protrudes .Not got a NA piston so I dont know where it stops ,I'll have to get one with a 73 crank ....
If I made the rod 5 mill shorter we'd be in the same stop position but compressing another 65 cc :devil: So how much shorter do I need to go ?
Std 7ZU ..Big end to little crs is 146 ,small end to piston top is 43 ,crank is 63 throw so cr to deck is 220.5 .
What I'm looking to do is put in a crank that is 73 .
So it's either custom rods or pistons ????
Safrane Bi-turbos are rarer than a610 and more expensive .I know that the last two crated units went for a lot of dosh .One was complete with turbos,loom ,even gearbox .It's in Ireland being plonked in a GTA.
I bet they are rare! :) Mad that it's going in a GTA. :agree:
http://www.carstyling.ru/resources/studio/94heuliez_renault_long_cours.jpg
Not much of a looker. :dearme:
i produced something very similar to that after a night of vindaloo abuse.
markey b
04-12-2008, 20:35
what was the renault 25 v6 turbo? think JP has one in his barn!
Exactly the same as the GTA .Z7U only in those two cars .
Some of the 25's had lower comp ratio of 8:1 due to a 2mm lower crown height but feck knows where they are .I was going to look at machining some of the std crown off .I think that'll be all they did as I can't see them making a thicker section for just a few motors ????
I've sliced a piston to see and it shouldn't cause much of an issue if you see where the thin area is ...This will give me about 46cc more as well :laugh:
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markey b
04-12-2008, 20:53
has anyone got a pic of half a 5 piston... mine are pretty dished and that pic scared me!!!
Markey Mark (BD)
04-12-2008, 20:58
has anyone got a pic of half a 5 piston... mine are pretty dished and that pic scared me!!!
I got a knackered 5 one which i might cut in half just to see how much meat is left on there once there falt topped or dished
markey b
04-12-2008, 21:01
i've got a spare piston, but nothing to cut it with, unless a junior hacksaw is up to the job lol
I did it with a normal hacksaw so a junior one should be fine on a iddy-biddy 5 piston :p
91 diameter ...about 7.5 mm thick at the radius to angle bit .....What's a 5s bore ??
just to go back to the objective.... what is it ? if your after making more power then you aught to be looking at the cylinder head and not CC's. You can only make as much power as the cylinder head will support, which I dare say is achievable within sensible rpm's at the current capacity. The cylinder heads are not that wonderfull :(
If you're after making some better midrange then that's different :)
I'm after more power .I don't want to lose too much low end torque .I have no beans to spend .
Given the RR result ,the next stage is the 60trim turbo ,330cc injectors and :agree:250 is possible on those rollers ???
It's very difficult to get any info on the Europa Cup GTA ...they're supposed to be 300 with not much different to a std Z7U lump ....but .......
Head work is wot per pot ?
New poster! (less than 10 posts)
just to go back to the objective.... what is it ? if your after making more power then you aught to be looking at the cylinder head and not CC's. You can only make as much power as the cylinder head will support, which I dare say is achievable within sensible rpm's at the current capacity. The cylinder heads are not that wonderfull :(
If you're after making some better midrange then that's different :)
True for NA motors, much less so for supercharged ones. Why do you think they supercharged the Mini Cooper S? The base chrysler engine was so rubbish the only way to get the performance they wanted was to blow it!!!
Back to your earlier question clee, 9:1 should be fine on a bar of boost. I'm sure the easiest way would be to use all the NA bits and machine about 1mm off the crown. Know its boring but you probably don't need any custom bits for this level of tune.
New poster! (less than 10 posts)
And as an aside, please promise me you're not going to use that exhaust manifold.....
New poster! (less than 10 posts)
True for NA motors, much less so for supercharged ones. Why do you think they supercharged the Mini Cooper S? The base chrysler engine was so rubbish the only way to get the performance they wanted was to blow it!!!
yeah, but that isn't really what I ment jim.
his power potential is the same regardless of cc's. If the cylinder head and camshafts havn't changed then it's potential to breath hasn't increased any. this is true of an FI engine too. it's ability to breath will ofcourse increase but only if he hasn't reached the limit of the cylinder head.
In the case of the GTA it's widely accepted that the cylinder heads are pretty crap. there is more potential in lee's engine which he can extract without extra cc's. I know his car, I mapped it, I know that when he fits his larger injectors and we run more boost that he'll make "some" more power but it will rapidly get to a point where more boost doesn't yeild extra power - that'll be the cylinder head and camshafts becoming the bottle neck. At this point more CC's won't help, and that was my point really.
The manifolds are the biggest restriction .Heads are ****e .
I'm up for any suggestions ,advice :)
I think we'll run out of grunt at the next level as Scoff says .But surely a 2.5l v6 should be capable of more .
I want to get more power but spend my money in the right place first time :laugh:
I think I've got a 3l crank sourced ,one of the less vocal Alpine guys has done some research ,mocked up a bottom end etc .He has some bits and pieces ,ideas .
3l heads might be OK ..My sort of price as well .....barter the parts bin :agree:
The 46cc is of course only the chamber increase or total volume increase. The swept area remains the same. So it stays as a 2.5 litre.
The 5GTT piston crown apparently is 13mm thick so there's plenty of metal left after taking off a couple of mm.
The 5GTT is 76mm bore IIRC which I may not.
.But surely a 2.5l v6 should be capable of more .
Don't forget the 2.8 inj engine in the Capri back in the day (1988), made a whopping 150bhp. Less than my old 1.6 CRX Vtec produced in 1991. Lol. :wasntme:
Surely quite a bit more torque though and where it's wanted.
Power is just torque x revs.
So if it won't rev it won't make so much power. But might still pull like a train at UK legal speeds.
Don't forget the 2.8 inj engine in the Capri back in the day (1988), made a whopping 150bhp. Less than my old 1.6 CRX Vtec produced in 1991. Lol. :wasntme:
I had one back in the day :o Then I had a TVR wedge with the same lump ...I know which one went better :laugh:
So if it won't rev it won't make so much power. But might still pull like a train at UK legal speeds.
What, all the way to 30 :laugh:
Sorry Ian, I'm just being facetious. What you assert about torque is spot on.
markey b
05-12-2008, 18:51
dunno if anyone wants to move this post... but i got a c1j piston cut down today
http://i11.photobucket.com/albums/a190/mark_wsmcuk/r5piston.jpg
lee, it might be interesting if you could collect the data of your own cam's plus any of the NA cam's you can find, it might be that some of the NA cam's are be better suited once you get the big turbo back on. :)
That's the problem .....finding the data . I sold a set of cams that were supposedly better for my needs ages ago before I knew owt ...2.8l espace or 25 :confused:
I can't remember but I did measure them at the time very roughly .David G had them off me and sold them on .I'll do some digging .
some of the time the printed data needs to be taken with a pinch of salt anyway since they probably won't tell you how they've measured it!
how about gather up some camshafts from likely donor engines as and when you come across them cheaply then meaure them in a spare block like andy did with the GTT camshafts.
I did write it down somewhere ....Argggh I hate it when that happens :laugh:
They had far more lift I think .
I did write it down somewhere ....Argggh I hate it when that happens :laugh:
They had far more lift I think .
the standard factory cams will be pretty mild things, they're designed to work with a poky little turbo. some NA cams might be a cheap winner. :cool:
Hey, I think scoff and I agree on something;). Seriously though take a look at the 3l cams, they've probably got the most aggressive profile (being from the largest engine and it needing to breathe through crap heads...). Unless, of course, there was a particularly sporty version.
I'm not doing a sales job here but getting your heads cleaned up and cams reprofiled is not going to break the bank, if they really are that much of a bottleneck it would make a big difference.
I think I should clear up that when I talk about power I generally mean an engines performance within its useable envelope. The peak number is nice to have and gives you a high top speed potential, but not much else. Know I'm not being completely semantically correct on this one, but there really is no substitute for cubes.
3l cams could be the winner then :)
I've got two sets of skimmed heads with cams and another complete Z7U .So plenty there to experiment with .I've got a N/A 3l block and crank coming in the post :laugh: did a swap from the parts bin :agree:
Volvo B280E ...highest lift and longest duration std cam .I want more power but for track use ,not strip .
How much is not much Jim ? PM me a rough idea .
The Venturi 260 is supposedly a 2.8l 7ZU with a 73 crank and custom pistons ....300ftlbs and 260 bhp @ a bar . I need to get this confirmed .
Found some data on the B28 Volvo cams :) I need to measure the std GTA lift but the timing is thus on the Z7U cam .
Inlet open 8 btdc
Inlet closes 40 abdc
Ex Open 40 bbdc
Ex closes 8 atdc
Volvo Cam ( it's odd fire but I think the lift will be similar to the B280E which is even )_ I think :confused::laugh:
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Andrew Cooke
09-12-2008, 18:20
Found some data on the B28 Volvo cams :) I need to measure the std GTA lift but the timing is thus on the Z7U cam .
Inlet open 8 btdc
Inlet closes 40 abdc
Ex Open 40 bbdc
Ex closes 8 atdc
Volvo Cam ( it's odd fire but I think the lift will be similar to the B280E which is even )_ I think :confused::laugh:
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take that data and throw it in the bin, it's meaningless. Measure everything, trust noone, they're all liars :laugh:
Yes,so I've been told :laugh:
If I measure the lift on my std cams can I trust myself :confused:
I have been known to feck things up now and then :wasntme:
Andrew Cooke
09-12-2008, 18:35
Yes,so I've been told :laugh:
If I measure the lift on my std cams can I trust myself :confused:
I have been known to feck things up now and then :wasntme:
actually, what you can see from the Volvo data is that the LSA is 106deg (I hope, I'm rushing here...), and it's timed straight up.
If you can't trust yourself put all your toys in a big box and stick them on Ebay ;)
I did work out out what LSA meant before I googled it :cool:
How you deduce the angle from the figures though escapes me :confused:
Must get boring measuring all those C1J cams Andy ? How about measuring some nice big v6 units to break the monotony :agree:
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0606em_camshaft_specs/lobe_seperation_angle.html
Andrew Cooke
09-12-2008, 19:21
I did work out out what LSA meant before I googled it :cool:
How you deduce the angle from the figures though escapes me :confused:
Must get boring measuring all those C1J cams Andy ? How about measuring some nice big v6 units to break the monotony :agree:
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0606em_camshaft_specs/lobe_seperation_angle.html
it gets a bit tedious, I've done an awful lot of them now:boring:
The main thing is to be consistent in your method, I think yours is OHC, I've done some EVO cams, and they were an arse as I had to modify it to solid tappet and shim the tappets. If you have adjustable tappets you just need to fit an inlet and exhaust valve with soft springs then plot the valve movement.
I just need to get a cam angle dial knocked up .I was going to put a clock on the valve top and watch when it moves :agree:But I hadn't thought to put a softer spring in :cool:
Would this be accurate enough ?
I have already jigged a head up after my valve clash issue ........
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Andrew Cooke
09-12-2008, 19:42
print
http://www.rtoc.org/files/Technical%20Files/Scoff/timing-disc.jpg
Woah!! Can you make that a bit bigger please, Andy?... I can't make it out...
'tis rather large innit :laugh: Good job I've got a 22 incher :p and a A1 plotter but i think it'll hide all the engine :confused:
Andrew Cooke
09-12-2008, 19:59
Woah!! Can you make that a bit bigger please, Andy?... I can't make it out...
it's that size for any member surfing on their phone;)
it's that size for any member surfing on their phone;)
Lol:laugh:
theyd b there a good hour b4 the page loaded lol :laugh:
Found some data on the B28 Volvo cams :) I need to measure the std GTA lift but the timing is thus on the Z7U cam .
Inlet open 8 btdc
Inlet closes 40 abdc
Ex Open 40 bbdc
Ex closes 8 atdc
Volvo Cam ( it's odd fire but I think the lift will be similar to the B280E which is even )_ I think :confused::laugh:
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So those are the lairiest std cams? No wonder these engines struggle. You could run a diesel on timing like that. If these engines do have poor heads then they will need duration duration and some more duration.... 228degs is never going to do it. I reckon as a start you would need some thing with about 30degs more on an LCA (Lobe Centreline Angle please, we're not American!) of about 110 with 0.040"ish LATDC. Then you might start seeing some power and still shouldn't be sacrificing midrange.
Andrew Cooke
10-12-2008, 13:15
So those are the lairiest std cams? No wonder these engines struggle. You could run a diesel on timing like that. If these engines do have poor heads then they will need duration duration and some more duration.... 228degs is never going to do it. I reckon as a start you would need some thing with about 30degs more on an LCA (Lobe Centreline Angle please, we're not American!) of about 110 with 0.040"ish LATDC. Then you might start seeing some power and still shouldn't be sacrificing midrange.
LCA is not the same as LSA... we're engineers ;)
how can you tell how much LATDC the cam he quoted has?
infact how can you tell how much duration the cam he quoted has?
which has more duration, a standard GTT cam, or a Piper 270?
which has more duration, a Kent RT200, or a Piper 285?
How can you tell?
You're gonna say ' by measurement ' aint ya :D
LCA is about 170 on one and 10 on the other ?Somewhere in those figures I'm sure there's a clue :confused:
Cam A
668
Cam B
670
Lee,,,,
if Rennie and Honda can get 1000BHP + out of a 1500cc.......sure we can do something for you Lee.....LOL..
now, the stroked crank isnt near enough to sort what you want......wrong configuration from what i have been told....
BUT, that doesnt stop you sorting a 2.9 V6 block....working the heads and making some in and out bits.....low comp pistons and your away... woo hooooo...
or......are you into a bit of bobandaconker tuning.......£50 =50BHP
It's ' 2bobanaconka Tuning ' I think you'll find :smokin:
It has to be paid for out of my little car bits and bobs innit .But I can draw stuff up and get it machined .Not forged pistons though ................or maybe I can ..
At some point I'm going to have to spend some money but I want to make sure it goes to the right place for the right bits .
Nothing is available off the shelf at all ,not even an uprated spring so it's research ,research, beg ,borrow and steal ( well ,so to speak )
Andrew Cooke
10-12-2008, 19:58
you can easily check the cam lift of those 2 cams
http://www.lunaticams.com/Tech/Cams/CamSpecTerms.aspx
0.170"
I'm sure the 2.8 lump cams I had were a good 60 to 80 thou more :cry:
Andrew Cooke
10-12-2008, 20:22
0.170"
I'm sure the 2.8 lump cams I had were a good 60 to 80 thou more :cry:
are you sure? that doesn't sound like much.
Base circle 1.190" over lobes 1.360 "
See what I'm up against :laugh:
I need a great pooling of minds and experience :agree:
Andrew Cooke
10-12-2008, 20:31
Base circle 1.190" over lobes 1.360 "
See what I'm up against :laugh:
I need a great pooling of minds and experience :agree:
:smashpc:
any idea what the rocker ratio is, and what size valves you have?
No idea on the rocker ratio ? How would I calc that from bench measurements ?
Valves are 44 mm in and 37 exhaust
Andrew Cooke
10-12-2008, 20:38
No idea on the rocker ratio ? How would I calc that from bench measurements ?
Valves are 44 mm in and 37 exhaust
you could fit the cam and measure how far the valve opens, compared to that .17 will give you the ratio.
Nice big valves, they'll love lift. How are the port diameters?
Inlet 34 ........Ex 30.................:eek:
I've got a few days off for pissing about in the garage so I'm going to set up a block,heads and **** for measuring
Andrew Cooke
10-12-2008, 20:55
Inlet 34 ........Ex 30.................:eek:
I've got a few days off for pissing about in the garage so I'm going to set up a block,heads and **** for measuring
is this engine out of a van?
It's the sexiest van you'll ever see .For all it's faults :smokin:
Andrew Cooke
10-12-2008, 20:59
It's the sexiest van you'll ever see .For all it's faults :smokin:
I suppose it can't be that different to the one my Dad had in his 265 Volvo Auto.
PRV .....Should have been a V8 but the oil crisis meant they lopped two cylinders off .Hence it's pretty unique as a 90 degree V6 :sad2:
I just want to get the best I can from it ...I don't want to move away from the PRV as it would no longer be a GTA .
LCA is not the same as LSA... we're engineers ;)
how can you tell how much LATDC the cam he quoted has?
infact how can you tell how much duration the cam he quoted has?
which has more duration, a standard GTT cam, or a Piper 270?
which has more duration, a Kent RT200, or a Piper 285?
How can you tell?
AS a non engineer then (;)) could you explain to me the difference between LSA and LCA?
Unless the figures quoted were at a specified checking height then as an educated guess I would say they had about 0.020" LATDC and also assuming (I know assume nothing, but you have to work with what you have...) that the figures given describe the designed valve motion events then 8+40+180=228.
I don't have the foggiest idea about the specifics of the cams you mention, but I know that a cam with the specs I mentioned will perform very well. :)
by the way, Honda NSX-90 deg V6, not really that unusual, just not common.
Do need to be careful with measuring rocker ratios. When the rocker is the follower, the observed ratio changes with the installed valve height.
LSA is how far apart (angle of seperation) the centre of the lobes are.
LCA is how far off centre/tdc the lobes are.
but you have to work with what you have...
thats rarther the point though jim, you don't have to, you can measure it. :)
LSA is how far apart (angle of seperation) the centre of the lobes are.
LCA is how far off centre/tdc the lobes are.
Sorry to disagree, but LCA is Lobe Centreline Angle ie the angle between the centreline of the lobes (more usefully taken as the crank angle between the center of max lift on the exh valve to the centre of max lift on the inlet valve) , nothing to do with distance from TDC. You can have a given LCA and time it anywhere you like in relation to the crank.
LSA is just an americanism for the same thing.
And yes Scoff, as usual you are absolutely right:( TNFG is a rule we should all live by. My point seems to be missed though. The valve timing specified for that volvo cam (unless it has massive and probably destructive valve acceleration - not likely) is never going to produce an particularly impressive power output.
Go on then... cam degrees not crank degrees
sure, I didn't look at the actual numbers :)
re the lsa business, lobe center is the real term, lca seems to have gotten lumped with the same definition somehow, I think I'd know what people ment whatever they called it ;)
Andrew Cooke
11-12-2008, 00:21
re the lsa business, lobe center is the real term, lca seems to have gotten lumped with the same definition somehow, I think I'd know what people ment whatever they called it ;)
LSA, or LCA, it's all academic with asymmetric cams as the angle changes depending upon the lift you measure it at. Once again, it's all lies :laugh:
LSA, or LCA, it's all academic with asymmetric cams as the angle changes depending upon the lift you measure it at. Once again, it's all lies :laugh:
what do you mean about the lift? (know what you're getting at with the lies bit!!!) the apparent centre might vary depending on your checking height, but surely the centre of max valve lift is the centre of max valve lift, a physical property of the cam:confused:
Andrew Cooke
11-12-2008, 19:23
what do you mean about the lift? (know what you're getting at with the lies bit!!!) the apparent centre might vary depending on your checking height, but surely the centre of max valve lift is the centre of max valve lift, a physical property of the cam:confused:
by lift I'm meaning checking height. So seat timing may give you 118deg LSA (:D), 20 thou 115deg, 1mm 110deg, peak lift 106deg, which one is going to give you the best feel of what the cam will do in an engine?
To my mind the angles between the absolute peaks isn't probably as important as the angles at which you see 1mm of valve lift. I've given up, and only worry about LATDC, then play with duration at 1mm valve lift. Maybe I'm right, maybe I'm wrong. Plotting out all those cams was very telling (btw, they will be back up on this site soon thanks to Scoff writing a sexy bit of software)
I'm liking that Hotrodding site ...It's a bit of a read so I'll have to do it in stages :confused:
http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/photo_05.html
by lift I'm meaning checking height. So seat timing may give you 118deg LSA (:D), 20 thou 115deg, 1mm 110deg, peak lift 106deg, which one is going to give you the best feel of what the cam will do in an engine?
To my mind the angles between the absolute peaks isn't probably as important as the angles at which you see 1mm of valve lift. I've given up, and only worry about LATDC, then play with duration at 1mm valve lift. Maybe I'm right, maybe I'm wrong. Plotting out all those cams was very telling (btw, they will be back up on this site soon thanks to Scoff writing a sexy bit of software)
Like I guess you've discovered, cams are a bit of a black art. For lower levels of tune, its all fairly basic but when you start going for it, everything interacts and nothing is simple. I tend to go for peak lift LSA(:laugh:) and LATDC, 40 or 50 thou checking heights miss out the lifting ramps, which is good for getting an idea of a profiles "area under curve" but how quick the valve gets off the seat can play a big part in how it behaves (along with everything else.....).
Talking to the cam grinder (even though it's all lies!) should let you know what a profile is intended for.
God I wish it was simple:crap:
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