High compression 4e?

[J25GTi]

Hey guys,

Im looking to go tdo4, and my engine builder has suggested that we should up the compression of the engine to get it spooling faster. 3.8k is far too late for driving around here, it will end me up in a hedge on my roof...

So,

Is this a good idea? whgat are the pros and cons of going high compression?

Want to make this spool as fast as possible, as the roads around here after data logging some RPM levels, seem that its 3 - 5.9k rpm most of the driving is done at, so dont want boost coming on in a corner!

 

[weakboy2]

will work ok, but you will find you wont be able to run huge boost as pre ignition will become a problem.

if most of your driving is within those rev ranges, i would suggest a hybrid would be a better choice.

 

[MarcoFTE]

Hybrid CT9 (or that new TONGS CT12) on 1.2 bar might be an idea?

 

[Fatman]

Pro's: More power, more response, better fuel economy, earlier spool

Con's: Decreased detonation threshold, unable to run as much boost, requires precise fuel and timing control (good ECU)

Higher compression will definitely be nicer to drive and can be perfectly reliable, however it will be less tolerant of high IAT's or bad fuel, you will definitely require a good tune on a capable ECU. It really depends on just how much you want to bump up the CR...

 

[J25GTi]

Hybrid CT9 (or that new TONGS CT12) on 1.2 bar might be an idea?

true, could i not get the tdo4 down below 3k, running 1.1bar of boost and up the compression? with head porting etc? i dont really understamd how compression etc affects stuff

 

[J25GTi]

Pro's: More power, more response, better fuel economy, earlier spool

Con's: Decreased detonation threshold, unable to run as much boost, requires precise fuel and timing control (good ECU)

Higher compression will definitely be nicer to drive and can be perfectly reliable, however it will be less tolerant of high IAT's or bad fuel, you will definitely require a good tune on a capable ECU. It really depends on just how much you want to bump up the CR...

Well, i dont really understand hwo it works, Im thinking a megasquirt isnt the best idea on this kind of setup, and am going to go for an Emerald K3, Mapped by the legendary Dave Walker :rockon:

How much boost would it be safe tor un etc?

 

[Ted]

you will never get a td04 spooling down there on a 4e. my engine has dished pistons and a 0.6mm trd head gasket. its pretty lively off boost must say. we recently mapped it at 1.5 bar on a vf24(bigger than a td04) and detonation wasnt an issue(it was at 1.6!) so plenty of scope for running a td04 at at least 1.5 on a high compression engine.

on a compression test my engine was 160psi across the board

 

[J25GTi]

you will never get a td04 spooling down there on a 4e. my engine has dished pistons and a 0.6mm trd head gasket. its pretty lively off boost must say. we recently mapped it at 1.5 bar on a vf24(bigger than a td04) and detonation wasnt an issue(it was at 1.6!) so plenty of scope for running a td04 at at least 1.5 on a high compression engine.

on a compression test my engine was 160psi across the board

I thought to raise the compression ratio you need to make the amount of space smaller, so bigger pistons not dished, headwork with a good skim etc, bigger headgasket etc will lower it?

the whole point is im trying to get it way down, because i have all the bits for it, even if i can get it down to 3k, which i dont see is impossible with headwork, high compression free flowing exhaust and filter?

 

[Fatman]

Impossible to say what sort of boost will be achievable without knowing what CR you're aiming for and how you're getting it.

I'll be running 1 bar or so on a 9.8:1 5e-fhe using water injection, it's been done before with excellent results. Water/meth injection is very valuable for keeping det at bay on high compression turbo builds.

If you want your turbo to spool earlier you need to look into optimising every aspect of the engine. Bigger exhaust will give better spool, decent intake, good manifold. Timing and fuel can also make a big difference in where a turbo will come in. I don't think you're going to get a td04 on full song by 3k even with everything perfect.

 

[Fatman]

you will never get a td04 spooling down there on a 4e. my engine has dished pistons and a 0.6mm trd head gasket. its pretty lively off boost must say. we recently mapped it at 1.5 bar on a vf24(bigger than a td04) and detonation wasnt an issue(it was at 1.6!) so plenty of scope for running a td04 at at least 1.5 on a high compression engine.

on a compression test my engine was 160psi across the board

Hate to rain on your parade but 160psi is less than the tired 20 year old 190,000km 4e-fte that I just pulled out of my GT measured at. Dished pistons are for lowering the effective compression ratio, a trd head gasket will raise it, but not enough to counter the difference from the pistons. You were certainly running below stock compression ratio.

 

[J25GTi]

Impossible to say what sort of boost will be achievable without knowing what CR you're aiming for and how you're getting it.

I'll be running 1 bar or so on a 9.8:1 5e-fhe using water injection, it's been done before with excellent results. Water/meth injection is very valuable for keeping det at bay on high compression turbo builds.

If you want your turbo to spool earlier you need to look into optimising every aspect of the engine. Bigger exhaust will give better spool, decent intake, good manifold. Timing and fuel can also make a big difference in where a turbo will come in. I don't think you're going to get a td04 on full song by 3k even with everything perfect.

i did hear him throwing around 10-1CR, if that sounds about right?

I honestly dont understand all this about compression ratio to be honest,

So what would be a better turbo to use if i cant get a tdo4 down that low? I want something that will give a bigger punch than the td12 hybrids, and as no one has got any power figures for the td12's i dont want to try it and find out its not what i want

 

[Fatman]

In all honesty if a td04 is too laggy then why bother changing from the CT9?

What are your power goals?

Somebody is bound to say go CT9 hybrid, personally I think they're a waste of time and I'd tell anybody considering one to go for a td04 anyway. The only other way to get a td04 spooling significantly quicker (other than going 5e, which is definitely going to give you the best results) would be to track down the smallest exhaust housing version, the name momentarily escapes me. They aren't particularly common (or popular for obvious reasons) but should provide a far larger kick up the bum than a CT9 without significantly more lag.

10:1 is HIGH for a turbo engine and I personally wouldn't recommend it.. in my case I'm doing it to (hopefully) demonstrate the capability of an unopened 5e. If I were building an engine to spec I would probably go for something a little lower, 9:1 or thereabouts. Still higher than a standard 4e-fte but low enough that with solid tuning it can still run a good quantity of boost (1 bar+)

 

[J25GTi]

Good man!

Well, power wise, im not too fussed about the figures, i just want a car that will be drveable, every day, wont run out of puff at 200 bhp, and will give quite a low down spool time, so i dont end up with a whack of 1bar of boost at 3.5k just as im going round a corner.

I dont want to stay ct9 as it just doesnt have enough puff, need something that will last and can be improved on fairly simply...

In all honesty if a td04 is too laggy then why bother changing from the CT9?

What are your power goals?

Somebody is bound to say go CT9 hybrid, personally I think they're a waste of time and I'd tell anybody considering one to go for a td04 anyway. The only other way to get a td04 spooling significantly quicker (other than going 5e, which is definitely going to give you the best results) would be to track down the smallest exhaust housing version, the name momentarily escapes me. They aren't particularly common (or popular for obvious reasons) but should provide a far larger kick up the bum than a CT9 without significantly more lag.

10:1 is HIGH for a turbo engine and I personally wouldn't recommend it.. in my case I'm doing it to (hopefully) demonstrate the capability of an unopened 5e. If I were building an engine to spec I would probably go for something a little lower, 9:1 or thereabouts. Still higher than a standard 4e-fte but low enough that with solid tuning it can still run a good quantity of boost (1 bar+)

 

[Sheldon]

you will never get a td04 spooling down there on a 4e. my engine has dished pistons and a 0.6mm trd head gasket. its pretty lively off boost must say. we recently mapped it at 1.5 bar on a vf24(bigger than a td04) and detonation wasnt an issue(it was at 1.6!) so plenty of scope for running a td04 at at least 1.5 on a high compression engine.

on a compression test my engine was 160psi across the board

hes saying upping the compression.. yours is lower then stock

 

[Fatman]

Good man!

Well, power wise, im not too fussed about the figures, i just want a car that will be drveable, every day, wont run out of puff at 200 bhp, and will give quite a low down spool time, so i dont end up with a whack of 1bar of boost at 3.5k just as im going round a corner.

I dont want to stay ct9 as it just doesnt have enough puff, need something that will last and can be improved on fairly simply...

You're definitely describing a td04.. If your only concern with spool time is from sudden power delivery mid corner then there are ways and means around that without reverting to a smaller turbo.

Some aftermarket ECU's (including the megasquirt) have boost by throttle position. You can map the desired boost level by how far open your throttle is. A common issue on boosted cars (especially with larger throttle bodies) is very binary power delivery, once the turbo is on song it's hard to regulate with the throttle. With the boost by throttle feature you have the ability to drop the boost back to say .5 bar at half throttle and can have it linearly increase with more throttle through to your maximum of 1bar.

I have driven a BIG turbo 4e with this feature and it's fantastic, you can accurately regulate the boost with your right foot, wheelspin is a thing of the past as you can dial back the power until you find some grip.

 

[Starbus]

We've turbo'd many cars with compression ratio's as high as 11.1:1. But if your looking to make an engine spool earlier your beating up the wrong bush IMO.

Heres what i'd be looking to change, in order;

Capacity
Turbo,
Cam's
Mapping
Compression ratio
Manifold
Boost pipes
Inlet manifold
Head work

Regards
Ricky

 

[J25GTi]

Yes i noticed that feature on the ECU, and i suppose with a good map i could bring it on boost sooner with different ignition timing etc.


3,800 RPM, i really dont see that 3k would be a problem with a properly sorted set up, head porting polishing, cams etc?

You're definitely describing a td04.. If your only concern with spool time is from sudden power delivery mid corner then there are ways and means around that without reverting to a smaller turbo.

Some aftermarket ECU's (including the megasquirt) have boost by throttle position. You can map the desired boost level by how far open your throttle is. A common issue on boosted cars (especially with larger throttle bodies) is very binary power delivery, once the turbo is on song it's hard to regulate with the throttle. With the boost by throttle feature you have the ability to drop the boost back to say .5 bar at half throttle and can have it linearly increase with more throttle through to your maximum of 1bar.

I have driven a BIG turbo 4e with this feature and it's fantastic, you can accurately regulate the boost with your right foot, wheelspin is a thing of the past as you can dial back the power until you find some grip.

 

[Fatman]

You will definitely struggle to get it to spool that low, even doing everything described. Either a smaller exhaust housing or a larger engine driving it will be the only really feasible ways of achieving your goal.

Compression does certainly play a role but it's unlikely to make up 800rpm.

 

[J25GTi]

You will definitely struggle to get it to spool that low, even doing everything described. Either a smaller exhaust housing or a larger engine driving it will be the only really feasible ways of achieving your goal.

Compression does certainly play a role but it's unlikely to make up 800rpm.

no i definatley understand compression alone wont, but with other mods etc i think it is possible,

dont suppose you know the name of the other tdo4 with the smaller exhaust housing?

same compressor side etc i suppose? so will have the same capabilities?

 

[weakboy2]

unlikely, unless you have some kind of hybrid, i think the td04 you are referring to is the td04-11b.

much like a hybrid ct9 tbh.