How to get more power?

[gardner51]

Hi all, in middle of rebuilding the engine of my 5 after it dropped a valve,

Have got a good thickness head that's going on which has had a little work done,

Also low comp pistons to make it safer to up the boost abit to,

I was running around 22psi on a t28, came out at about 195hp, maybe furling wasn't 100% but I will be fitting a afr gauge to get this spot on this time,

But I find with the t28 I get a lot of lag. Comes in at 5k-ish,

I am wanting around 250hp, how would I see this? What else can I do?

Elliott

[Os8472]

What cam are you using?
Down pipe?
Exhaust system?
Intercooler/charge cooler?

[gardner51]

Sorry was abit basic,

Running a 285 cam,
2 1/2 down pipe,
2.5" exhaust system,
Front mount intercooler,

I was running a grill mounted intercooler but was making the car run to hot. Wasn't letting enough air into the rad.

Elliott

[Brigsy]

Wouldnt bother with low comp pistons personally mate, you wont need them.

[5teve L]

250 is hard to get to without alot of work & time setting things up & OK in a drag car for short bursts, not in a road car IMO... 200 is about the max for a road car(again IMO) without it popping liners all the time. You will need to be running high comp or alot of boost to reach 250 on a carb.

Unless you go Efi, which makes it alot easier to set up

[gttjames]

Ellz i think you should aim for a real 220/230bhp - as should be achievable.

It has got the enlarged downpipe, but standard elbow - power to be had here?

I think the way your going with it is right, keep pistons as you have it, good rebuilt head. And 24psi if you can fuel for it - should see 220bhp if its all set up ok, what do you think guys?

Also the problem your going to have like you have now is emptying the carb. Need a improvement here. Im not sure what to do here, better fuel pump? adjustable fpr?

[gttjames]

What cam are you using?
Down pipe?
Exhaust system?
Intercooler/charge cooler?

cam is a 285
its a 2.5 inch ktec downpipe jobby but with standard elbow off turbo
2.5 inch rest of system, and like ellz has said hes done a fmic

head he has is standard thickness and going to have valves re lapped and piper springs fitted

[tubbyG]

Ditching my phase1 pump and fitting a much better fuel pump(meant for efi ) solved my bowl emptying issue at 22psi, and thats using the std fpr and 2mm needle valve.

[markey b]

30psi....

[Os8472]

cam is a 285
its a 2.5 inch ktec downpipe jobby but with standard elbow off turbo
2.5 inch rest of system, and like ellz has said hes done a fmic

head he has is standard thickness and going to have valves re lapped and piper springs fitted

Ditch the standard elbow and ktec down pipe for a one piece 2 1/2" job would be a good start, give the carb a bloody clean up and service. Refresh the fuel pump and regulator then wind up the boost.

What have you got your cam dialed in at?

[danielmk323]

I am wanting around 250hp

you want 250 bhp mean flywheel power or 250 in the wheels there is a big difference

[Ian S]

Estimated engine power. Not power at the wheels.

To get that power you'll need to get it all dialled in and properly adjusted with the cam, ignition and fuelling optimised. It's not just about bolting stuff on.

Low comp, 30+ psi, a bored carb and fuel injector will get you that but it'll be very poor off boost and hard to drive on the road.

[danielmk323]

Hi all, in middle of rebuilding the engine of my 5 after it dropped a valve,

Have got a good thickness head that's going on which has had a little work done,

Also low comp pistons to make it safer to up the boost abit to,

I was running around 22psi on a t28, came out at about 195hp, maybe furling wasn't 100% but I will be fitting a afr gauge to get this spot on this time,

But I find with the t28 I get a lot of lag. Comes in at 5k-ish,

I am wanting around 250hp, how would I see this? What else can I do?

Elliott

what t28 you have ?

[gardner51]

Not to sure... Took some quick snaps. Hasn't got a size on the rear?

[tubbyG]

Rear ar number will be inside where the turbo bolts to the manifold

[Dave Reed]

But I find with the t28 I get a lot of lag. Comes in at 5k-ish



That must be horrible to drive! You'll be needing a smaller rear housing (49) that should see you on boost by around 3.5k which is much better.. It will also make good power..

Sounds like you've got all the right bits so far (barring the rear of the turbo that is) so now it's just a matter of tunning it to perfection..
Also if you've dropped a valve you must be revving it way to much, its not always about revs, it's more a useable power band.. I never used to rev mine past 7.5k and only really took it to that when in the heat of a battle

If your funds can stretch I'd go for an aftermarket ignition control if poss, one with an injector output, that will sort out fuelling problems that you will get trying to run the carb.

[Slim]

ive been in a few other 5's and have had 2 different t28s including a rollerbearing one. Ive never seen one reach fullboost anywhere before 4.5. Mine starts boosting around 3.5 but kicks full about 4.5 no earlier


edit: with both a .49 and a machined out t2 .35

[Dave Reed]

ive been in a few other 5's and have had 2 different t28s including a rollerbearing one. Ive never seen one reach fullboost anywhere before 4.5. Mine starts boosting around 3.5 but kicks full about 4.5 no earlier


edit: with both a .49 and a machined out t2 .35

Shame you never came out in mine then as that had nearly 0 lag and that was a t28 rb with a 49 rear

[Tony Walker]

Shame you never came out in mine then as that had nearly 0 lag and that was a t28 rb with a 49 rear

Nos is a luxury :-)

[Dave Reed]

Nos is a luxury :-)

Lol y does everyone always thing that when u run nos that is constantly on

[tubbyG]

Dave, im intrigued - excluding the odd blast of NOS, what do you think aided low-lag in your setup?

fancy exhaust manifold, cam timing, comp ratio??..... all?

im seeing full boost by 4/4.5 k on my T28..... tbh I quite like the lag. if I wanna go rapido, I just rev and rev and rev

[Tony Walker]

Lol y does everyone always thing that when u run nos that is constantly on

What other magic spools a t28 with no lag?

[Tony Walker]

mines spikes to around 20psi at 4k then settles on 18ish.

[BILLY-R5GTT]

Have you thought about a good T25 instead? Your boost will come in alot sooner...

(plus you could sell me your T28 for my F7R turbo conversion )

[Dave Reed]

What other magic spools a t28 with no lag?

No magic required lol.. Just a good setup

It's all about getting everything to work together.. Cam timing affects a lot also ignition timing.. As said I never really liked to rev mine too much so always dialled the cam in on the marks, but that was with my trick cam not the norm 285... It was much better with the efi too..

Re the 0 lag, I was saying that I think getting full boost by 3.5ish k not to be lag... But then my engine had loads of work carried out to the head, again which would of helped...

[Logg]

Sounds like people are getting the boost threshold of a turbo and lag confused.

Boost threshold is what rpm you engine needs to make full boost.

Lag is the amount of time once past the boost threshold it takes for to produce max boost

A good example would of been my old T3 set up. I had full boost from just past 3k but it was quite a laggy and max boost would only be produced one in longer gears unless I was being very aggressive with the car.

Where as my current turbo has the same boost threshold of 3k but without any lag what so ever.

Just my 2pence.

Andy

[TNT ANDY]

Sounds like people are getting the boost threshold of a turbo and lag confused.

Boost threshold is what rpm you engine needs to make full boost.

Lag is the amount of time once past the boost threshold it takes for to produce max boost

A good example would of been my old T3 set up. I had full boost from just past 3k but it was quite a laggy and max boost would only be produced one in longer gears unless I was being very aggressive with the car.

Where as my current turbo has the same boost threshold of 3k but without any lag what so ever.

Just my 2pence.

Andy

4.11AM - are you a burglar?

[Logg]

4.11AM - are you a burglar?

For some reason this popped into my head damn now I'm hungry.



Now this is so far off topic better get the tomtom out to find our way back.

[GTphil]

As has been said, it appears you have most of the correct bits for good power, a full 2 1/2" downpipe would be much better imo.

You need to have a t28 with a .49 exhaust housing and but even that is a very vague discription, the trim size is important also, I'm not hugly up on turbo sizes but I think 60 trim is what you want.

for the record my t28 starts to spool at 3.5k and is at full boost by 4.5k I run a standard downpipe and I'm lead to belive that larger dpwnpipes reduce lag.

Then it's all about the tune,

Fuel
Boost
Ignition
cam timing
And how well you can get the engine to breath high up the revs.

People say that headwork is pointless, but my brothers engine is an old bb tuning lump thats has loads and I mean loads of headwork and it breaths really well high up the revs and continues to make power beyond 7.5k rpm, where as mine with a standard head and downpipe makes more power (bigger turbo/more boost) but starts to choke up past 6.5k rpm and won't make any more power.

As has been mentioned above mappable ignition makes a huge difference and after that efi.

For me on a carb past 230hp and your on risky ground, ok for short bursts but not prolonged lead foot syndrome.

For that the set up needs to be 110% and I would even go as far as to say forged pistons steel rods and a multi layered head gasket, there was an engine built by Glenn HI5 Off here that I have heard storys of it bouncing off the limiter in fifth gear doing unmentionable speeds at 30+ psi so it is possable but kind of depends how far your wallet can strech

[gardner51]

Cheers for all the info. I'm going to rebuild with what I have. Then get the fuelling sorted so its spot on. Then maybe go for a smaller rear housing if mines not a .49 already. Witch I'm sure it isn't as it takes ages for it to spool up,

Elliott

[gttjames]

yer good choice i think mate. For 230+ i think yourl have to spend alot of money. Where as the setup you have allready, maybe a few other bits like .49 rear, and fuel pump will see good power

[gardner51]

Just been to look at the turbo. It has a 64 rear, so I will get a 49 rear, this will make it spool quicker?

Ellz

[THE MASTER]

build an engine that's good bhp then add a turbo to it best way foward

[m5tt]

In regards to the T28 subject, can you purchase a t28 with a .49 rear or is this something that you need to do yourself?.