Fundamental 2JZGTE flaw?

[Chiefgroover]

Yeah I've been in a slower scoobie that felt WAY faster. When I demo my car I always tell the passenger to watch the speedo and not the road!

John sounds like a Skyline with mega sticky rubber is a good alernative, wow those can hold on!.

[JohnA]

Even BPU Auto Supra's I've been in dont feel particularly fast, despite getting to 120mph very quickly, its such a smooth drive its deceptive.

 

Ah, that's the excuse I came up with as well.

 

So I fitted the accelerometer now and the 'seat-of-pants' dyno was proven correct.

Hell, I've done 0-60 in 2.x and know what is fast and what isn't.

Today I got it flat out at 17psi (and very low temps before/after turbo) and while it was nippier than before it didn't exactly scare the life out of me (at high 5s it's no wonder)

[JohnA]

...John sounds like a Skyline with mega sticky rubber is a good alernative, wow those can hold on!.

funnily enough I had a well-sorted skyline of a friend in that same 'test track' with the same accelerometer.

It did easily a 5.1 with both of us blokes in (no underfed ballerinas!) with crap rear tyres and 1.1bar

 

If I were to push it and smell some clutch (1.5K it cost him I think fitted, lol) I'm sure we'd see high 4s no probs.

 

Hello?!

[Bobbeh]

I guess you should go back to the Calibra if its McLaren F1 beating times you want.....

[JohnA]

I guess you should go back to the Calibra if its McLaren F1 beating times you want.....

The calibra fell apart mate, Rust In Peace, build quality was eeeerrmmm...questionable

 

F1 beating? don't think so, but straight 5s it would do, bless its heart...

[Bobbeh]

I remember the 4x4 Calibra was rated at 5.5 secs.. a very nippy car. Again, modded no doubt it'll be little quicker, but 4WD is gonna get a better launch unless you're gonna be running Drag Radials or something.

 

Did you ever take your Calibra to the drag strip?

[JohnA]

5.5?

nah...book figure for stock was 6.2 for 0-60, but I doubt you can do that if you're not a dragrace midget with free clutch-swapping services.

 

I've got a friend coming on Sunday, he's building a 400+ 4x4 calibra, currently mapping and rebuilding for the Nth time

 

If it runs OK we might give it a go for old time's sake

Did you ever take your Calibra to the drag strip?

nope

wouldn't trust it to rape it at the Pod and stay in one piece to bring me back home. Ah, those were the dayz...

[Bobbeh]

Hehe, I've seen it published somewhere before.. but tbh, you got 5.7 with your Supra? I've seen 5.5 listed as a common 0-60 time for a UK auto, so I wouldnt worry about it I bet you can get it lower with different tyres/surface and all sorts of crap, your car will really come into its own over 60!

 

Its not a power thing restricting your 0-60, its just getting the traction.

[JohnA]

...I've seen 5.5 listed as a common 0-60 time for a UK auto, so I wouldnt worry about it ..

When I bought the car I didn't bother doing any measurements because I was under the impession that the turbo(s) were broken and didn't want to damage it further.

Turns out it was all in my fertile paranoid imagination, the car was fine, as soon as I fitted a boost gauge it went straight to 10-11psi and stayed there.

 

But I didn't have any 'stock' figures, and I don't trust manufacturers' figures either, that's why I asked for people's own 0-60 times, so I could 'calibrate' my own times.

 

But I'm none the wiser, without powerbraking etc I don't see it doing 5.5 at stock boost and auto mode.

[Chiefgroover]

Have to say, we all like a bit of G-Forces, have you had a run in a "big" Supra?

[JohnA]

nope

[Branners]

Calibra 16v red top = 150bhp

calibra 16v turbo = 200bhp

 

any manufacturer that puts out a car with double the base power due to a turbo has to be very sure of reliability and also be very sure the thick twats that buy the car dont throw it off the road and claim it was too powerful

 

Has to be said UK spec compared to j-spec is quite different. Push 17psi in a j-spec and it feels considerably quicker. Put the UK spec in true twin mode and at 17psi you can really feel the kick. I still think the auto is better matched to a j-spec than a UK spec.

 

JB

[JohnA]

we've slowly drifted away from the question behind this thread, which is the punny 10bhp/psi offered by the 2JZGTE.

 

John, I am not comparing n/a vs turbo versions as they come from the factory, because they don't fit the bill out of the box.

 

In order for the x2 factor to be valid, everything has to be adjusted for smooth operation at 1 bar, and the intake temps have to be ambient.

Standard OEM offerings rarely meet these criteria, especially when they come with laughably punny intercoolers. The vauxhall engine at 1 bar with intercooling bringing charge temps down to ambient can see 270bhp without yet optimising anything else.

 

In stock form I measured 100C post i/c on a summer's day 5 years ago. Hardly a setup to be used for comparisons with theoretical maximums, eh?

[Digsy]

Quote:

Originally Posted by JohnA

Even in stock trim, the TT runs 10-11psi max, which is roughly 2/3 bar.

Operating parameters are pretty optimised at that level, so one would reasonably expect 220bhp + (2/3)*(220bhp) = 360+bhp, way more than the real figures..

 

Quote:

Originally Posted by Digsy

...If you factor up the GE's max power by using the final pressure calc, I reckon you get something pretty close to the real figures: 362hp @ 0.75 bar boost (11psi) for a stock UK car.

 

 

Do you see a similarity in the figures above?

Yeah but hang on a mo...

 

When I wrote that I was under the impression that the UK spec Supra had a bona fide 350bhp under the hood - turns out I was wrong, its 326bhp.

 

Yes, your calc and mine agree at this point, but as I said above if you want to factor power up by boost pressure then you have to normalise the 2JZ-GE's power up to 27bhp at atmospheric pressure in the manifold, thenapply the factoring up by your boost pressure.

 

Without wanting to appear pedantic, 11psi is just over 0.75 bar, not 0.66 bar, so by your calcs the GTE power should be 220 x 1.75 = 385hp

 

If you (as I think you should) assume the GE makes max power at a VE of less than 100% (say 80%) then the GTE's power will be (220 / 0.8) x 1.75 = 481

 

However, this gives you a power of 360 ish hp at 1.75 bar, which I now know is too high.

 

If you set the VE at which the GE makes 220hp to 89% (still not outlandish - the throttle will be wide open after all) then power at 1.75 bar manifold pressure using the final compression formula will be 326hp, which is spot on for a UK spec. OK, so I used "goal seek" to find the manifold pressure / VE that woud work but by factoring on boost alone you will be 16% too high and by factoring on boost with correction for VE you will still be 25% too high.

 

I still think that factoring on boost pressure alone gives over-optimistic power fugures at high pressures due to the constant % error - it might be a better rule of thumb at lower pressure or lower powers. To be perfectly honest I have no idea whather the final compression formula is really any better, but I'm assuming that the in-cylinder pressure at the end of the compression stroke must be proportional to torque and, therefore (assuming the same engine speed) proportioinal to power. It just seems more likely than ignoring the geometric CR differences between NA and turbo, and factoring on charge pressure aone.

 

I don't think there is anythng much wrong with the GTE's design - by my way of reckoning you woud be getting in the region of 380hp at 1 bar boost, which is unsurprisingly well short of the 440 you expected to get.

Factored power.zip

[JohnA]

Without wanting to appear pedantic, 11psi is just over 0.75 bar, not 0.66 bar, so by your calcs the GTE power should be 220 x 1.75 = 385hp.

Is the standard max boost with both turbos supposed to be 10 or 11psi, I'm not sure. Mine was sitting at 10, but spring chicken it wasn't.

I treat 10psi as 2/3 of a bar, which roughly is 15psi. This still doesn't change these 'ballpark' calculations -- which appear to work fine for other engines, like the RB26 for example.

If you (as I think you should) assume the GE makes max power at a VE of less than 100% (say 80%) then the GTE's power will be (220 / 0.8) x 1.75 = 481.

maybe the GE makes max power at 80% VE, maybe at 90% (with all that variable intake stuff). I still don't buy that the turbocharged version of the engine will make 100%VE at 0psi boost. Empirically I know that this is too optimistic, it never happens in this sort of engines.

However, this gives you a power of 360 ish hp at 1.75 bar, which I now know is too high..

dito

If you set the VE at which the GE makes 220hp to 89% (still not outlandish - the throttle will be wide open after all) then power at 1.75 bar manifold pressure using the final compression formula will be 326hp, which is spot on for a UK spec. .

Interesting

but if you drive a turbocharged engine making sure that you never exceed the '0 psi' point on the boost gauge, it will be nowhere near as fast as the n/a version flat out.

So this could be a red herring.

 

I still think that factoring on boost pressure alone gives over-optimistic power fugures at high pressures due to the constant % error - it might be a better rule of thumb at lower pressure or lower powers. .

We've already said that.

You have to make sure that all parameters are normalised for operation at that boost level.

You'd need to totally redesign an engine to have such operation at 2 or 3 bar boost pressures. Charge temps would be the easiest of problems to solve actually, cam timing and ignition would be harder to get right.

 

but I'm assuming that the in-cylinder pressure at the end of the compression stroke must be proportional to torque and, therefore (assuming the same engine speed) proportioinal to power. .

Bad assumption.

max in-cyl pressures are NOT proportional to torque, or power when it comes to forced induction. That's the whole point!

In a n/a engine, the only way to double power (once you can't raise VE any more) is to either double the revs or double the cyl pressures - or variations of the theme, you get the picture

In forced induction you don't need to do either, you get away with mildly increasing cyl pressures, but you can do that over a longer part of the power stroke. So you get double the area under the curve, without nasty pressure peaks.

 

 

 

By the way, this rough power calculation method is not something I made up yesterday, it is standard practice in forced induction.

Which is why I am perplexed with the 2JZGTE's performance.

[chilli]

Interesting post, from a simplistic point of view I think the assumption you started with is flawed because a stock N/A engine is more highly tuned than a TT engine and so would deliver more power than the TT running at 0bar boost. So I don't think the argument holds up.

 

also, as has been said, the theoretical 1bar = twice the power is a "best case" maximum, not a nominal or expected value. Start with the maximum, work backwards factoring in losses and I think it's certainly not a flaw in the 2JZ-GTE set up.

 

My old integrale ran around 210 bhp at 0.8 bar, it gave about 270 bhp at 1.2 bar, according to what you are saying it should have given 315 bhp at this pressure, again this is not a flaw in the engine.

[JohnA]

...a stock N/A engine is more highly tuned than a TT engine and so would deliver more power than the TT running at 0bar boost. So I don't think the argument holds up.

I've already mentioned this twice in this thread mate, looks like you've missed it.

 

also, as has been said, the theoretical 1bar = twice the power is a "best case" maximum, not a nominal or expected value.

I've also laid down the conditions for this, more than once.

Does nobody read the posts properly anymore?

 

My old integrale ran around 210 bhp at 0.8 bar, it gave about 270 bhp at 1.2 bar, according to what you are saying it should have given 315 bhp at this pressure, again this is not a flaw in the engine.

I am pretty sure that you just skimmed though the posts, rather than read them carefully mate.

Did you optimise anything for your 1.2 bar operation? Were the charge temps ambient for example? Did you make ANY changes apart from raising the boost?

If not, this is not a relevant example (I was hoping to make this distinction clear from my first post, with not much success apparently )

[chilli]

Well it was a skim read to some extent, for that I appologise. Then again, I am allowed to have the same opinion as you, I was just stating my opinion to add to the mix Sorry if that offended anyone and sorry for any duplication of information. The reason I posted is that there seemed to be a whole topic of conversation started from a flawed assumption. The Integrale was was remapped with a new ECU but ran on a standard intercooler.

[JohnA]

.... The reason I posted is that there seemed to be a whole topic of conversation started from a flawed assumption. .

I wish that the assumption were flawed mate, you know like those mathematical puzzles that force you to think the wrong way.

 

As I said, this thinking is standard practice in forced induction design, I didn't cobble it up last night

..The Integrale was was remapped with a new ECU but ran on a standard intercooler.

exactly. I was nowhere near as 'optimal' at 1.2 bar as a n/a version of the engine would have been at full throttle operation.

 

It's not easy to get it optimal at 1.2 bar, you'd have to reduce the static CR for one, properly, with low-comp pistons. Then the cams would have to change, dialled in a bit perhaps too. A different turbo would be needed, to account for the new airflow and re-set the backpressure for the new balance.

THEN fuelling and ignition would be mapped on top. Intercooling would have to be seriously enhanced as well.

 

ONLY THEN would one have the liberty of applying the multiplication factor to the n/a engine and compare the results. (OEMs tend to do it like this usually, especially in non-budget designs)

[Digsy]

John, just for clarity, are you saying that you have optimised all the parameters for operation at 1 bar of boost, and you aren't getting anywhere near your theoretical 440hp?

[chilli]

I understand what you are saying, but have you reduced your CR and matched everything else so carefully, only then would you be able to claim that you should get close to the theoretical maximum, otherwise thats just life. Still big gains for little effort though, personally I'd be happy, especially since it's so easy to tune compared to a N/A!

[JohnA]

John, just for clarity, are you saying that you have optimised all the parameters for operation at 1 bar of boost, and you aren't getting anywhere near your theoretical 440hp?

 

I'm saying that the 2JZGTE only manages 10bhp/psi from the factory turbocharging [(326bhp -220bhp)/11psi ] where I'd expect it to be closer to 15bhp/psi.

[JohnA]

...only then would you be able to claim that you should get close to the theoretical maximum, otherwise thats just life.

 

but we've already repeated that several times on this thread, haven't we?

 

In real life due to practical (and cost) considerations we can only approximate so much to the theoretical maximum.

In my experience, good designs double this n/a figure at about 1.1bar (the extra 1.5psi makes up for the unoptimised 'leeway')

 

This 'quest' for me has started ever since I bought my first spanking new turbo, a 1984 Kawasaki 750t (unloved and deserted in a dealer's showroom ever since someone left a deposit and never went back to buy it)

The n/a version of that engine, the ZX750 of that era, was pumping out 80odd horses (I think) while the kickass 'turbo' version 112 horses.

I went through every tuning book I could get my hands on (this was way before the internet era) trying to figure out where all that boost went. I did find out the truth eventually through experimentation. That's another long story in it's own right.

Still big gains for little effort though, personally I'd be happy, especially since it's so easy to tune compared to a N/A!

Oh yes, no questions there mate

From the current breed of engines available it is the daddy for high-bhp DIY tuning

[chilli]

Yeah I think it's been covered one way or another here.

 

Also, don't forget, pure BHP would most certainly have not been the primary design goal for the car.

 

they gave us a twin turbo sequential turbo set up for driveability, not for bhp, a single would have done for that - and so on and so forth.

 

I expect in order to give a driveable amount of torque low down in the rev range the set up is not optimised for bhp alone, and for this I think they made the right choice!

 

Also, the Jap market with its gentlemans agreement of 280bhp, I'm sure Toyota's R&D and marketing department knew what was best at the time. We know the car is capable of much more

[Digsy]

I'm saying that the 2JZGTE only manages 10bhp/psi from the factory turbocharging [(326bhp -220bhp)/11psi ] where I'd expect it to be closer to 15bhp/psi.

Based on this?

 

Most 2 litre engines of recent design (1990->) are close to 10bhp/psi

A 3 litre engine of similar pedigree should be at 15bhp/psi.

The 2JZGTE is not an overblown 4 cylinder engine, so we don't expect efficiency losses due to grotesque combustion chambers or cylinder size.

It is 86x86mm, with an excellent head design.

 

The C20LET (opel) engine is also 86x86 with similar head design. At 1 bar held boost it produces 290bhp/290lbft, which is almost double that of it's n/a derivative (C20XE, 150bhp)

So we're talking 10bhp/psi without any fancy stuff, just optimal intercooling and sorted fuelling.

The GM fam2 turbo in factory trim ony makes 5 hp/psi - forget the VX installation - this is an engine dyno figure from when it did its power certification. As JB pointed out it makes the same in the Calibra.

 

You cannot imply that because you reckon to be able to get 300hp at 1 bar from home tuning, GM should be able to get 15hp/psi from the 2JZ in stock trim.

 

Surely the question should be: Why aren't GM making more like 7hp/psi from their stock 2-litre, as opposed to only 5? Stock trim versus stock trim - that would be comparing apples with apples.