View Full Version : quick with a standard turbo...thoughts.
over the years and with trying various turbo's, i always found that the gt appeared to be quicker off the mark with a standard turbo and standard cam. however after messing about with revvy cams and losing peaks of torque. i figured that a very standard cam but with monster lift, might be a better way to go?
surely it would aid spooling of the standard cam, and give plenty of midrange punch- without having to rev much past 6500rpm (new bottom end anyone?) ???
Maybe a silly question but not sure what you mean when you say "std cam with monster lift".
Am I right in thinking a high lift cam just leaves the valves open for a longer period of time? When changing from a std cam to a performance cam does anything change other than the duration that the valves are open?
well, I'd agree.....as Renault spent a lot of time and money developing the cam used...
also, PM the wizard...he's great help with questions like this...LOL...:agree:
i mean a cam with standard duration (how long the valve stays upen) but with extra lift ( how far the valves are pushed open). performance cams change both. but generally its the duration increases that increases the rev range.
Maybe a silly question but not sure what you mean when you say "std cam with monster lift".
Am I right in thinking a high lift cam just leaves the valves open for a longer period of time? When changing from a std cam to a performance cam does anything change other than the duration that the valves are open?
Andrew Cooke
01-07-2009, 17:41
i mean a cam with standard duration (how long the valve stays upen) but with extra lift ( how far the valves are pushed open). performance cams change both. but generally its the duration increases that increases the rev range.
oh, you mean like the Piper 270?
think this could be possible looking from the point of view that the valve is staying open the same time but is allowing the cylinder to be filled to the brim with fuel and air since the valve is opening "more" and allow more of the mixture in......
oh, you mean like the Piper 270?
i was thinking abit more lift than that. :) ...but yes, it did pop into my head.
Andrew Cooke
01-07-2009, 22:05
i was thinking abit more lift than that. :) ...but yes, it did pop into my head.
you won't get more lift than that with standard duration.
I don't think you'll improve the standard cam with the standard turbo in place, you are ultimately limited by the turbo's ability, or lack of. Look at how much better the standard cam works with a bigger turbo - evidence that the cam really isn't a problem at sub 160hp, which is all you can realistically expect from the standard turbo. Any gain is going to be marginal and at the expence of drivability.
over the years and with trying various turbo's, i always found that the gt appeared to be quicker off the mark with a standard turbo and standard cam. however after messing about with revvy cams and losing peaks of torque. i figured that a very standard cam but with monster lift, might be a better way to go?
surely it would aid spooling of the standard cam, and give plenty of midrange punch- without having to rev much past 6500rpm (new bottom end anyone?) ???
Alternatively, fit a vernier pulley & dial in some cam advance to aid spool-up.
Edit. Just re-read what you meant - Perhaps a bit of cam retard would raise the peak torque rpm, but the bottleneck is still gonna be the turbine.
In reality though, even throwing trackday driving into the equation, do you really need to rev the engine that high? If you want power, you're back to bigger turbos & cams again, but that's straying off the original idea.
it was just something that popped into my head when i sold my silver gtt. i built a standard engine and fitted a standard turbo to it, and was pleased with the immediate throttle response and 'get up and go' it had. i wondered if there was a way to improve this, without the lagginess, and with a VNT.
markey b
01-07-2009, 23:26
Raise the c/r
thats what mike48 did when he built mine (for biggs)
raised c/r std cam and vnt
Matt Cole
02-07-2009, 13:14
I wonder how much power you could get out of the engine before turbo charging?
Dale 21T
02-07-2009, 13:22
my old 1 made 179 wiv the t2 @18psi! only a few bits done filter, group a carb, zost from downpipe bak! ran ok for nearly 2 years :D
Andrew Cooke
02-07-2009, 13:27
I wonder how much power you could get out of the engine before turbo charging?
depends how much nitrous you fancy squirting through it :D
markey b
02-07-2009, 15:22
depends how much nitrous you fancy squirting through it :D
or what kinda supercharger you use :wasntme:
I wonder how much power you could get out of the engine before turbo charging?
i think you would struggling to make anywhere near 90bhp with the low comp.
how do you go about turning a turbo charged reading into a n/a reading regarding bhp. is there any mathermatics or is it guestimate.
100 bhp turbo= what na
Standard turbo'd c1j's made 115bhp in the ph1 and 120bhp in the ph2, the standard N/A c1j made 60bhp but the c2j which only had a twin throat carb over the c1j made 72bhp, the N/A gordini engine made 90bhp but that had a cross flow head and 10-1 compression ratio.
I'm in the process of building a high compression N/A c1j for my bro's triumph spitfire, yeah I'm stuck with the non cross flow head but it'll have 9-1 compression, twin SU carbs, the bigger GTT valved head and a few other little tricks, we're hoping for around 95bhp, should be possible but it'll be built with as many GTT parts as poss so it can rev to 7grand all day :D
Matt Cole
02-07-2009, 20:22
yeah what i meant was taking the cij and tuning it to the max in n/a form. Then bolt the turbo on and go from there.
yeah what i meant was taking the cij and tuning it to the max in n/a form. Then bolt the turbo on and go from there.
its a different form of tunning on N/A to turbo... if you want more more on N/A you get twin carbs, solid lifters with high cam, high compression etc etc with turbo you want to get the compression lower so you can run more boost... so different kettle of fish really :D one of the best things ive seen someone do (to a saxo vts) was to sleeve down the cylinder size from a 1.6 to a 1.4 and it had good power gains... dont know how will find link to spec later on
yeah what i meant was taking the cij and tuning it to the max in n/a form. Then bolt the turbo on and go from there.
as dave says, totally different way of thinking matt. for instance, in n/a land you'd be looking to use cam duration in conjunction with the exhaust headers to create scavenge. that scavenge would be anhialted the second you bolted the turbo on, and instead of making power the lairy cam would end up costing you power instead.
Matt Cole
02-07-2009, 21:37
its a different form of tunning on N/A to turbo... if you want more more on N/A you get twin carbs, solid lifters with high cam, high compression etc etc with turbo you want to get the compression lower so you can run more boost... so different kettle of fish really :D one of the best things ive seen someone do (to a saxo vts) was to sleeve down the cylinder size from a 1.6 to a 1.4 and it had good power gains... dont know how will find link to spec later on
:agree: doh my lengthy reply has buggered up:cry:
Matt Cole
02-07-2009, 21:42
It went something like this:
Most n/a engines respond very well to bolting a turbo on with standard n/a cam and slightly lower compression. Yes you cant run a bagfull of boost on a high comp engine reliably, but on average a standard n/a engine can run moderate boost withought any big engine mods. For reliability take the 172 for instance compression 11:1(i think) down to 9:1, 9 psi of boost, adjusted fueling and a decent turbo and you have a dam good power increase. I'll not mention BHP figuers with fear of being shot down, but its an idication of what can be had from a manufactured n/a engine. The gt has imo a very low compression base, why? who knows possibly due to reliability or maybe due to the cubic capacity which i think maybe it doesnt need to be so low. I would like to see someone up the compression and use the n/a cam (timing adjusted to suit) or similar spec, get it fueling and revving well test its output as a comparison and then force feed it (again with corrective fueling and ignition) and test it against a mega boost gt. This is for a road going car and not a drag monster tho. :)
:agree: doh my lengthy reply has buggered up:cry:
lol ><
Matt Cole
02-07-2009, 21:44
reply to dave scoff and not your good self;)
matt, yes, see what you are saying. You'd still run into problems with a lot of n/a cams and the tiny restrictive T2 though, even the c1j or c2j cam might be a little too wild to have any gain with a standard turbo, like I said in my first post. Now then, fit a decent turbo and it's a whole different story as you well know :)
I've said it for years, anyone running less than 18psi (ish) should increase compression ratio, it makes a huge difference! But no, people fit those silly blue mellior gaskets, dropping compression because of it's height and removing the only fusability the engine had with the "propper" gasket inplace. It's backward thinking. I don't think you'd get as far as 9:1 though, you'd do well to run 15/16psi without knock at that.
what cam does Col run in the camparse?
what cam does Col run in the camparse?
standard 1390cc campus I bet, but then he isn't using a T2 ;)
Matt Cole
02-07-2009, 22:06
matt, yes, see what you are saying. You'd still run into problems with a lot of n/a cams and the tiny restrictive T2 though, even the c1j or c2j cam might be a little too wild to have any gain with a standard turbo, like I said in my first post. Now then, fit a decent turbo and it's a whole different story as you well know :)
I've said it for years, anyone running less than 18psi (ish) should increase compression ratio, it makes a huge difference! But no, people fit those silly blue mellior gaskets, dropping compression because of it's height and removing the only fusability the engine had with the "propper" gasket inplace. It's backward thinking. I don't think you'd get as far as 9:1 though, you'd do well to run 15/16psi without knock at that.
Agreed on the T2 matey, although the topic of this thread is about using the T2, i was infact refering to a 'decent' turbo in general. I guess getting the most from the setup whatever the components would be needed. On to my next point, albeit slightly relevant is the difference between the 225 and the 172 engines. The cams in the 225 are 'supposedly' different to the 172's, engineered by renault to be more suited to the turbocharging as is the difference between n/a and turbo engine camshafts normally. Also there are measured differences within the head and valves. Again i don't know this for certain but from research and conversation.Thing is if it was as simple as bolting a turbo on and lowering the compression to suit, i don't understand why these differences are required? Is it down to reliability?
I've said it for years, anyone running less than 18psi (ish) should increase compression ratio, it makes a huge difference! But no, people fit those silly blue mellior gaskets, dropping compression because of it's height and removing the only fusability the engine had with the "propper" gasket inplace.
:agree:
Rob@Backyardracing
02-07-2009, 22:28
i really think the gtt needs to have a 16v head fitted, someones gotta try it, with a decent inlet mani, and it will make good power. the head is old fashioned, and out-dated compared to modern heads, i dont think the pistons, or CR are anywhere near as important as the head in terms of making hp. the pistons only really contain, and transfer the energy to the crank, but the head is responsable for much more like delivering, and removing the gases quickly and efficently, the optimum velocity of the gases, being able to maintain the highest amount of timing, or CR, without knock etc.
imo the gtt has to run such a low CR, because the head is such a poor design, and has little tolerance to knock. (ok its not bad compared to other old motors, ford pinto anyone? lol) but modern motors run much higher CR then the older siblings, evo`s, hondas ect, can all easily run 9.1 and still lotsss of boost with no problems. i know of hondas running 45psi at 10.1 cr!! thats a head!
forget the cam is what im saying, change the head :)
we all like abit of head ;) thou really dont we... ;) lol
Agreed on the T2 matey, although the topic of this thread is about using the T2, i was infact refering to a 'decent' turbo in general. I guess getting the most from the setup whatever the components would be needed. On to my next point, albeit slightly relevant is the difference between the 225 and the 172 engines. The cams in the 225 are 'supposedly' different to the 172's, engineered by renault to be more suited to the turbocharging as is the difference between n/a and turbo engine camshafts normally. Also there are measured differences within the head and valves. Again i don't know this for certain but from research and conversation.Thing is if it was as simple as bolting a turbo on and lowering the compression to suit, i don't understand why these differences are required? Is it down to reliability?
Ah well, the answer lies in something I said above about cam duration and the effects of duration when you bolt a restrictor in the exhaust path (turbo).
broadly speaking, once you add a turbo to an engine it's ability to run cam duration (more so overlap) diminishes. 172 will have wilder cams with more overlap than the 225 engine. The 172 cams in NA form will make more power than the 225 cams in NA form, we know this, but add a tiny turbo into the mix and the 225 cams will be the winners because their profiles are such that they will work better with a restrictive exhaust than the 172 profiles would.
I can get away with 172 camshafts in my engine because the turbo is huge, it doesn't pose the restriction that the 225's turbo does. The less restriction you have in the turbine the more wild a cam you can use, you get closer to NA ways of tuning. If you were to fit a big old blower to that 225 engine of your's you could install 172 camshafts and see a big increase in performance, no doubt.
Rob, in the nicest way, I have to disagree mate.
The combustion/squish chamber of modern turbo engines is more resiliant to detonation than the old crumby design of the c1j 8v head. That, and the fact that most, if not all, are now efi, thus better fuel control per cylinder, plus a dedicated ignition (re)map for a given fuel quality, far superior knock control, and a more efficient/higher o/p HT circuit, and it's like comparing chalk & cheese.
Imho, the head isn't the problem. Sure, it's not as efficient as could be, and an extra 8v would go a long way, but at the end of the day the air is still being forced in/through regardless, and given in this instance that we're only referring to running a T2 blower, the gains of modifying the head for that application would equate to minimal.
In all the years rtoc/gttoc has been running, no-one has found mouth-watering gains from modifying the head. That either means they've made a hash of a job (possibly), or the fact, that more than likely, is that the overall gains were/are minimal.
Like Scoff, I've always said that a high c/r is the way to go if you can control the detonation. The problem there, going back to the start of this post, is that you're relying on a carb and a pretty much fixed ignition map for det' suppressant.
Matt Cole
02-07-2009, 22:55
Good info Scoff, so to summarise, fitting a larger turbo with my cams will only see gains up to a certain point. After that, changing the cams and upping the turbo again will offer even better gains?
Nice;)
Good info Scoff, so to summarise, fitting a larger turbo with my cams will only see gains up to a certain point. After that, changing the cams and upping the turbo again will offer even better gains?
Nice;)
pretty much :) everything has to work together, so if one component changes drastically then the rest needs to follow suit in order to see things at their potential.
Duncan Grier
02-07-2009, 22:59
:yeahthat:
And not just the Renault world ;)
this been a good topic lots of good views and info in here... good read :D
Standard turbo'd c1j's made 115bhp in the ph1 and 120bhp in the ph2, the standard N/A c1j made 60bhp but the c2j which only had a twin throat carb over the c1j made 72bhp, the N/A gordini engine made 90bhp but that had a cross flow head and 10-1 compression ratio.
I'm in the process of building a high compression N/A c1j for my bro's triumph spitfire, yeah I'm stuck with the non cross flow head but it'll have 9-1 compression, twin SU carbs, the bigger GTT valved head and a few other little tricks, we're hoping for around 95bhp, should be possible but it'll be built with as many GTT parts as poss so it can rev to 7grand all day :D
i made a 1397cc engine for my mk1, using a gordini block, extra van pistons, and a TL 1.1 head. - the valves were the same size as gtt ones. - the cam was a NA piper 285 (288 duration). it ran 11.2:1 compression and didnt pop.... unfortunately i couldnt get a twin shoke, so i was lumbered with a gt carb, jetted for N/A application. - it went, and is still going well! :D
next owner from me at the local 'races' 'http://www.youtube.com/watch?v=Wg2k0rKWpcQ
as for the 16v head idea, does anyone remember the guy from america? - R-sport who allegedly was working on a 16v head to stick on his Alliance? - he chuntered on about it being a suzuki (swift?)head, and how he was running the cams in reverse.....
i thought new engines didnt suffer fom detonation so much due to the ecu systems constantly monitoring knock, and retarding the ignition for each cylinder as an when it happens. - im sure if you stuck a gt's ignition system and a carb on most of these jap engines, they wouldnt last as well as you'd expect.....
I do love it when a topic gets all the big power boys going :D
I've oftern wonder how much of a difference a decent head design would make but getting a 16v head to fit will be a bitch but when you think about Renault already did somit better than the GTT head, the gordini cross flow, those lucky gits who have them, have decent gains in power over the GTT head just cus of its cross flow nature and the fact it has alot larger valves, end of the dy there ain't enough gordini heads out there, so until someone starts making brand new 1's we've gotta stick with the GTT head and focus on other ways of making power, like raising the compression as Scoff said
i'd say theres plenty of gordini heads out there for people who want to do the conversion (if you want a head and the other bits needed let me know ive got a couple). But its the rest of the work/money involved that will put people off. Its not a cheap conversion for the power gain both manifolds will need to be custom made. It would be cheaper to fit and turbo a 172 engine or the 1.8 16v from the clio/19 which will still give a better power increase and allow for further power in the long run.
Andrew Cooke
03-07-2009, 13:21
i'd say theres plenty of gordini heads out there for people who want to do the conversion (if you want a head and the other bits needed let me know ive got a couple). But its the rest of the work/money involved that will put people off. Its not a cheap conversion for the power gain both manifolds will need to be custom made. It would be cheaper to fit and turbo a 172 engine or the 1.8 16v from the clio/19 which will still give a better power increase and allow for further power in the long run.
:agree:
don't forget the volvo turbo option..
Rob@Backyardracing
03-07-2009, 18:27
i thought new engines didnt suffer fom detonation so much due to the ecu systems constantly monitoring knock, and retarding the ignition for each cylinder as an when it happens. - im sure if you stuck a gt's ignition system and a carb on most of these jap engines, they wouldnt last as well as you'd expect.....
that maybe true for some modern turbo motors, with COP systems, but our honda uses a plain old dizzy, and we have no knock control at all! so i really believe its not electrical as to its resiliance to knock, but the design of the head, including the squish area. even if you put a super modern high power COP system on a gtt, and EFI, i still dont believe it would be able to run anywhere near as much boost, or timing as a modern (ish) 16v head`d motor, i.e a honda head.
and the fact no-one has seen any dramatic gains messing with the stock head, is because the **** inlet mani and carb has still been in the way, and there is only so much you can do with the ports/valves.
look at A series mini`s, they make sod all power, and there are all sorts of heads on offer for those, with varying levels of modification, but theres also a 16v bmw head conversion available now (i think its from a bike?) and thats blows the A series heads away! same block, same pistons.....
Andrew Cooke
03-07-2009, 18:39
next owner from me at the local 'races' 'http://www.youtube.com/watch?v=Wg2k0rKWpcQ
cripes, I lived in Lea Marston when Hams Hall was a power station, I wouldn't recognise it now
Andrew Cooke
03-07-2009, 18:58
I would like to see someone up the compression and use the n/a cam (timing adjusted to suit) or similar spec, get it fueling and revving well test its output as a comparison and then force feed it (again with corrective fueling and ignition) and test it against a mega boost gt. This is for a road going car and not a drag monster tho. :)
all that glitters is not bling..
http://www.rtoc.org/cam/?cam=std+GTT&lsa=&cam2=C3J+NA&lsa2=&rocker=1.5&advance=0&vc=0.2
i thought the c2j cam was supposed to be longer duration?
rob- there is no doubt the honda engines are in another league for flow over the poor gtt head.lol
i think it was a bike head they fitted onto a mini block, im sure it was a bmw bike head.
what cam does Col run in the camparse?
mine :)
cripes, I lived in Lea Marston when Hams Hall was a power station, I wouldn't recognise it now
yeah, its quite the street racing hotspot now.
i thought the c2j cam was supposed to be longer duration?
Now thats interesting, I may have to look into one of those for me bros engine
Now thats interesting, I may have to look into one of those for me bros engine
open the link that andy posted. only lsa that is different.
Andrew Cooke
05-07-2009, 16:39
open the link that andy posted. only lsa that is different.
no idea what a C2J cam is, that was a C3J, no idea if that's different or not, but Miller thought it would be an improvement on a GTT cam and had the good sense to let me measure it first, as it came out it has less duration than the GTT cam, and would have been a backwards step. If I learnt one thing from measuring all those cams, it was to trust noone and measure everything.
As an aside I measured a cam of Rob@backyard, same duration as the GTT cam I had but with more lift, this leads me to believe that not all std GTT cams are the same.
open the link that andy posted. only lsa that is different.
Thats a very handy little link that, I like it, will come in very handy
As an aside I measured a cam of Rob@backyard, same duration as the GTT cam I had but with more lift, this leads me to believe that not all std GTT cams are the same.
back about 9 years ago, i distinctly remember GT Tuning selling uprated cams, that were supposed to be the same as standard cams but with higher lift - at least that what the word on the street was.
back about 9 years ago, i distinctly remember GT Tuning selling uprated cams, that were supposed to be the same as standard cams but with higher lift - at least that what the word on the street was.
i also heard that but at the same time remember roly praising the standard
cam an would not use anything else..was that used in b5gtt?..who knows..
:scratch:
Andrew Cooke
06-07-2009, 00:17
back about 9 years ago, i distinctly remember GT Tuning selling uprated cams, that were supposed to be the same as standard cams but with higher lift - at least that what the word on the street was.
it's possible, Rob thought it may be an EP cam, seemed too mild to me for that. Maybe GT Tuning were talking about the piper 270? that would fit the description. Any idea why a PH2 makes 120hp and a PH1 115? I wish I'd measured my cup cam before getting it cut, that would have been the best of the standard cams as it was an expensive Prima lump (no woodruf key in the crank to allow the timing to be tweeked...)
Any idea why a PH2 makes 120hp and a PH1 115?
allegedly due to the different ignition map...but i've never been totally convinced.
allegedly due to the different ignition map...but i've never been totally convinced.
I believe body coloured bumpers give you another 5bhp actually
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