Fundamental 2JZGTE flaw?

[JohnA]

I don't think anyone on here is going to get too scared by density and i/c effectiveness, it's not like we are all completely thick lol

It's not thickness, rather bad faith and a hostile attitude I can't explain.

Anyway, we digress...

[Digsy]

 

I wouldn't mind if you could email me that spreadsheet, I could compare it with others I've made in the past.

Unfortunately I can't send it to anyone, or post it up here. I did ask whether that would be possible, but the answer was no.

 

However, I have pretty much already written down how to do the simple stuff anyway, and like I said, if your intercooler is running an efficiency of 1 you can forget about the clever thermodymanics bits.

 

If you want to add those in, then the calcs for turbo and intercooler effects on density ratio can be derived from page 405 in the Bosch book (or rather a mate's Bosch book because I never got around to buying one myself )

 

Sorry for the blatant cop-out.

 

Incidentally, the 33% to 50% "frictional" losses also account for heat energy rejected to coolant and oil. It's kind of a "total losses" factor, which goes some way to explaining why it is so high.

[JohnA]

Unfortunately I can't send it to anyone, or post it up here. I did ask whether that would be possible, but the answer was no.

no probs, I too am picky with whom I share my computer models.

... if your intercooler is running an efficiency of 1 you can forget about the clever thermodymanics bits.

my intercooling is a bit over 1, on a 25C day 15-20C before the throttle at 1 bar.

Compressor efficiency is also very high (can't tell if it's over 100, but it's not improbable)

 

Incidentally, the 33% to 50% "frictional" losses also account for heat energy rejected to coolant and oil. It's kind of a "total losses" factor, which goes some way to explaining why it is so high.

yeah, that's well known, only one third of the fuel's chemical energy makes it to the crank.

[Digsy]

The digsmeister does it again...quite amazing how much frictional loss there is.

 

FWIW I don't think any IC core I've seen has ever claimed to be more than 92% (.92 out of 1) efficient...and most are high 70's to low 80's.

I can't take much credit for this one - I'm lucky to have a pressure charging guru a short walk away from my desk.

 

We need to be a bit careful about quoting intercooler efficiencies. The spreadsheet I'm looking at uses a different definition to the Bosch book. The spreadsheet defines intercooling effectiveness as the % of the extra heat added by the turbo that it removes (so 1 [or 100%] ) means it cools back to ambient.

 

The Bosch book defines intercooler rate or efficiency as the ratio of temperature after the intercooler to the temperature before the intercooler, so 1 = no intercooling.

 

I'm guessing that the figures Alex has seen relate more closely to the former, as anything over about 0.8 for the latter method gives cooling below ambient, which is impossible for a traditional intercooler.

 

[Alex]

no probs, I too am picky with whom I share my computer models.

 

It's not pickiness it's much more legally involved than that! But I'll let you carry on blindly thinking it's cause of people on here...yada yada...hell quoting this will give you another chance to have a go.

 

my intercooling is a bit over 1, on a 25C day 15-20C before the throttle at 1 bar.

Compressor efficiency is also very high (can't tell if it's over 100, but it's not improbable)

 

You cannot have a lower temperature after the intercooler than the ambient air temperature without additional heat rejection methods (WI/CO2 Spray etc) being employed. You cannot have a core that can chill to less than the temp of the air passing it by.

[chilli]

You cannot have a lower temperature after the intercooler than the ambient air temperature without additional heat rejection methods (WI/CO2 Spray etc) being employed. You cannot have a core that can chill to less than the temp of the air passing it by.

 

Yeah wouldn't that be akin to a perpetual motion machine aka getting something for nothing? A 100% efficient cooler surely returns the air to the temp of the cooler itself, which in an ideal world is ambient - unless as you say other cooling mechanisms are used. Even then its still to the temp of the cooler body, just that the body could be less than ambient with a heat pump, evaporator or similar to cool it down further.

[JohnA]

Yeah wouldn't that be akin to a perpetual motion machine aka getting something for nothing? .

Digsy doesn't wonder though, does he? Maybe because he bothered to read the first posts...

[chilli]

I'm not sure I follow you I'm afraid... Sounds like you trying to make a dig, at me, for not reading the posts. Still not sure what that has to do with the quote. Can you enlighten me/us?

[Digsy]

John has assumed perfect conditions for his scaling calcs - one of those being a "perfect" intercooler which returns charge temps to ambient.

 

He has also eluded to using some kind of evaporative system to bring the temps down even further.

[chilli]

yeah I can see that Digsy, I think early in the thread it was mentioned that he was eluding to an "ideal world" theoretical maximum.

 

I was just wondering exactly the tone of his last reply, since dry text alone does not convey all the message I think.

[Alex]

John, Try wording your post correctly to prevent ambiguity then, as it seems to the rest of the world that you are talking only about IC efficiency.

 

This WHOLE thread is about STOCK efficiency...if you're going to move the goal posts with every post then it becomes worthless/futile.

 

In your first post you say "post-intercooler temps near ambient" and in you last but one you say "my intercooling is a bit over 1, on a 25C day 15-20C before the throttle at 1 bar" the latter implies that you have better than 100% cooling efficiency via an intercooler and the former is meaning less.

[JohnA]

I'm not sure I follow you I'm afraid... Sounds like you trying to make a dig, at me, for not reading the posts. Still not sure what that has to do with the quote. Can you enlighten me/us?

First page dude, I even stuck the 'applause' smilie.

 

Every single word in my technical posts is there for a reason. For example, if I say 'intercooling efficiency' you should not assume that I meant 'intercooler efficiency' because it is not the same thing.

[chilli]

Well JohnA you've highlighted exactly the ambiguity Alex talks about then, in your very own postings.

 

you say:

 

>"I can and I do use such methods to get full boost temps down to ambient."

 

and then you say:

 

>"my intercooling is a bit over 1, on a 25C day 15-20C before the throttle at 1 bar"

 

which is not ambient...

 

and then you say

 

>"Every single word in my technical posts is there for a reason"

 

I think this thread will go around in circles and up its own proverbial a-hole if you are not careful.

 

I sense some unnecessary "chip on your shoulder" hostility from you John, why is that?

 

I think we are all only trying to help and understand better, we are all pretty much in the same boat after all. None of us worked in the Toyota R&D dept when they designed it (did we?).

[JohnA]

...

>"my intercooling is a bit over 1, on a 25C day 15-20C before the throttle at 1 bar"

 

which is not ambient...

 

if ambient is 25C how could 15-20C be also ambient?

It would be below ambient.

But this is not directly relevant to this thread (the question is why 10bhp/psi when it should be 15bhp/psi?)

 

It is a general question, irrelevant to my own setup at the moment.

 

I sense some unnecessary "chip on your shoulder" hostility from you John, why is that?

Not hostility mate, and certainly not you

 

There have been characters on this board who have tried to play 'keyboard warrior' in the past - you know, throw insults that they'd think twice if the communication was in person.

That's the reason behind the 'disclaimer' in the first post of this thread. But it didn't work.

[Bobbeh]

A lot of what he John says is cool, but I still think hes clinging on to his Calibra too much.

[JohnA]

The car at the back is a Calibra

http://www.max-boost.co.uk/stuff/CalibraCopCar.jpg

[chilli]

>if ambient is 25C how could 15-20C be also ambient? It would be below ambient.

 

Exactly, this conflicts the earlier statement:

 

>"I can and I do use such methods to get full boost temps down to ambient."

 

That was my point. I'm only here to discuss and learn, not to argue pointlessly, that’s for sure.

 

>Not hostility mate, and certainly not you

 

Ok well that’s good to know, plain text on the screen can easily be misinterpreted as there is no tone and sometimes very little context...

 

So just to clarify, the question you pose is, why on the stock set up do we see only 10bhp/psi boost - and so 100% or higher intercoolers don't really count since they move the goal posts don't they.

[JohnA]

Exactly, this conflicts the earlier statement:

 

>"I can and I do use such methods to get full boost temps down to ambient."

It doesn't conflict because they are not related to the question.

My own car hasn't got a fixed spec either, it changes every few days, I tweak and test stuff as a matter of course.

 

...So just to clarify, the question you pose is, why on the stock set up do we see only 10bhp/psi boost -

Do you want me to count the number of times I've repeated that during this thread?

Please tell me that this is a windup....

[chilli]

lol well then there is no need to cloud the issue with perfect intercoolers then (or your own personal intercooler setup).

 

stock set up doesnt have one, bhp/psi will be less than ideal for this alone, let alone the "other" losses that Digsy has done the best job of highlighting...

 

PS: the statements conflict each other, I never said they conflicted the question too...

[JohnA]

...stock set up doesnt have one, bhp/psi will be less than ideal for this alone....

That's the whole point mate: The stock setup at 10psi should be very close to the ideal:

 

1. CR is lowered to the ideal figure. (8.5:1 is excellent for a chamber like this one running 10psi boost)

 

2. intercooling is pretty much spot on (at 10psi the SMIC is very close to ambient on the road)

 

3. fuelling is not lacking (note the wording )

 

4. ignition is pretty much spot on (provided fuel of adequate octane rating is used)

 

Then why does it need 10-11psi for an extra measly 100bhp? It should be getting an extra 150bhp at that boost.

 

The mummy returns...

[Alex]

5. Cams don't breathe well enough...extrapolate a plot on a dyno sheet for an engine with no breathing limitations at high revs....

6. And the Frictional losses Digsy has mentioned.

 

 

(Oops sorry am I posting in your thread again after you told me in a PM not to? Sorry your PM must have been ambiguous, like your whole thread...oh hang on is that a goal post you're carrying there...)

[Ian C]

So can someone who knows what they are talking about post up a summation yet?

 

Hey - here is an interesting twist. I bet my bhp/psi is a lot different to a stock car (it'd have to be!), so surely it also comes down to turbo sizing? And by inference, charge temps?

 

Incidentally, anyone and everyone is welcome to post on this thread, and other technical ones, as long as it's relatively on-topic and not wildly offensive. If anyone has a problem with a post there is a "report post" button. Pm'ing someone because you don't like them pointing out perceived flaws in your argument is perfectly allowable too, just don't expect them to comply

 

-Ian

[JohnA]

So can someone who knows what they are talking about post up a summation yet?

 

here you go:

 

why does it need 10-11psi for an extra measly 100bhp?

[JohnA]

Another avenue to explore might be suboptimal performance of one of the manifolds --- inlet or exhaust.

 

Intake:

Flowbench figures would be nice, if anybody happens to have any available, ideally measuring the whole manifold at once under modest boost.

What I suspect is that maybe the designers found out (at a late stage perhaps) that under real-life conditions the airflow among the runners varies quite a bit under boost, with some cylinders getting more air than others.

On a mass-produced car they have to allow for variances in general, and when adjusting the fuelling maps they'd have to play it safe and allow for the cylinder with the highest airflow (for example cyl #6)

 

This would help that cylinder have the correct (safe more likely) AFR, but it would lead to every other cylinder being richer, with the one that flows the least amount of air running the richest of them all.

If the airflow variance is in the region of 10%, then after we've added 'safety' margins etc, we're talking of some seriously rich running cylinders here.

 

The manifold airflow theory can be verified if someone bothers to tap a 'nipple' at the end of each runner and then fit a boost/vacuum gauge on each one (similar to what we do for synchronisation of multi-throttlebody setups)

 

The variable 'richness' theory can be verified by fitting a pre-turbo oxygen sensor on each individual runner (not likely to happen outside an R&D department)

 

Tapping individual EGT sensors on the runners would give some indirect indication of an AFR variance.

 

Exhaust:

Toyota designers went out of their way on this engine trying to squeeze the last drop of energy from the exhaust gases. As a result exh backpressure is abnormally high throughout the whole revrange (ever wondered why fully decatted sequential TTs are still not too loud?)

As a result, a lot of gases stay crammed inside various exh pipes for longer than is normal (for a traditionally turbocharged engine)

 

Packaging restrictions have led to some 'strange' shapes of these exh pipes. Remember that these gases are very-very hot as they pass through the exh valves, and the oddly-shaped exhaust manifold might be creating unexpected resonances.

 

From the exh gases' point of view the shape of the exh piping varies according to the position on the EBV and the EGCV. Sometimes it's easy to go through the 'connecting' pipe, sometimes it isn't:

http://www.max-boost.co.uk/stuff/exhaust_path_connector_pipe.gif

 

During low-rev operation for example, imagine how different the exh path is for cyl #4 (blue) compared to cyl#2 (red):

http://www.max-boost.co.uk/stuff/exhaust_path_2vs4.gif

 

What about the exh gases trapped between the exh manifold and the EGCV (when shut)? Can they create harmonics that slow down the flow of cylinders 4,5 and 6?

http://www.max-boost.co.uk/stuff/exhaust_path_stagnant.gif

 

 

OK, for maximum power this is not as relevant, because all valves are wide open at that point, but the shape of the exhaust pipes is still odd, and the exh camlobes are all the same, they don't account for cylinder variations (as far as I know!)

 

 

Just some thoughts for anyone else intrigued by this bhp/psi discrepancy....

 

 

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[eyefi]

i'm still a bit unsure of why you expect 15bhp/psi. is it because of the extra 50% capacity over the 2litre (10hp/psi + 50% = 15hp/psi)?

 

Can you explain your logic here?

 

Cheers.