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22B said:
those figures quoted are at 2.1 bar.

This is running 97 ron super, not race fuel, with NF octane boost in a concentration of 1ml per litre.

Well, that would be pointless, as 0.1% conc of anything won't make any noticeable change to ocatane rating. Add some toluene or race gas in part mix. 2.1bar is way too much for SUL petrol, on any engine.

As for retard of ignition, this losses so much power, surely it would be worthwhile to cure the det problem at it's soucre rather than bothe with this?

BTW, this is not, in any way a flame towards you, just some constructive, and hopefully helpful criticism. :)
 

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"As for retard of ignition, this losses so much power"

The loss depends on how much of the timing is retarded. You just can't make a blanket statement saying any retarding your going to lose X amount of bhp, since we do not know if its going to be dropped 2* or 15*.

I would imagine 22B will have this all worked out when it was mapped anyways.
 

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Valve Train Efficiency

Hi all thought I'd butt in here! :D

I have seen an electromagnetic valve train in operation. Now adding that system to any car would get the damn thing singing its heart out....

Basically a computer tells the magnets to open the valves so far and for so long, low down the rev range they can be set to produce more torque then way up the revrange you could have all the lift and duration you need for ultimate power....

The technology is out there....unfortunately you need to miniturise it to make it fit under the bonnet!

As for displacement....bollox to it...My 2JZ has too much! I would (given the chance) bore it out by 1.5mm's but then reduce the stroke by 1.5-2mm's...thus allowing it to run at higher revs...7,000rpm is far too low for a sports cars engine :D. 9,000rpm would be very very nice!
 

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Re: Re: OK folks it is a long one.

Syed Shah said:


This is true, on most examples, such as the Supra and Skyline...

Hi Syed!

You know what the most powerful piston engines in the world are? Archaic single cam pushrod V8's with large (but not exceessive) bores and fairl mild rod/stroke ratios; admittedly they run nitromethane (top fuel drag cars) but if you apply the same principles to an engine running road fuel the possibilites are almost endless. How do you fancy a 600 cubic inch supercharged V8 with 2000bhp at 7000rpm and a torque "curve" which makes any turbo charged engine look silly - ie over 1000lb/ft of torque from 1000rpm upwards.
It's all readily achievable without needing totally exotic engine parts - a good forged steel bottom end which is professionaly balanced, topnotch pistons, and a well mapped EFI system. AFAIK the only cars to break into the 6's over the 1/4 mile are big V8's; even a bog stock 8 litre V8 with iron heads will make 700+ bhp on pump fuel if you bolt on a supercharger and a suitable cam, doubling that figure is simply a matter of spending money on a good quaity bottom end and a pair of nice alloy heads.

Technology can sometimes offset the advantage of displacement, but if you want big power then you need a bent eight, seven litres plus. Technology combined with displacement creates the best results of course :D
 

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Must admit I have to agree.

Although I reckon when it comes to piston engines, some of the steam or diesel cruise ships probably have a little more power :D but I am being facetious.

Problem with your theory is, if your aims arent drag racing then you have to work within the limits of your engine bay. I cant fit in a v8, and on top of that I wouldnt want to. I need to make sure the car isnt front heavy which it might be with steel v8.

I need it to handle.
 

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My V8 weighs in at 500lbs, not to bad. What does the RB26DETT weigh, I know Sean mentioned it is so heavy that it will bend a engine stand.

Now a Hemi will come in at 700-750lbs, but its a big block. Straight line is name on the game, they are right at home 6 sec 1/4. Then again, I know of 5.0 in the 6s as well.

22B, your engine should be way lighter I know.
 

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Just picked up on this thread.

Noticed the boost figures being quoted by 22b, and they are absolute boost pressure. Does everyone realise this?

I know it was in the formula, as such but anyway.

"Efficiency" is

1. the Volumetric Efficiency, that is, how much fresh inlet charge gets sucked in compared to the swept volume.
2. thermal efficiency, that is, how much of the energy from the fuel is converted to pressure, and ultimately mechanical power.

On high speed normally aspirated engines, VE can reach 120%, due to the momentum of the inlet charge, causing compression, at just the right time you close the inlet valves. Obviously at low speed, the valves will have been closed too late, causing inlet to be pushed out the inlet. And there you have the cam profile dilema in a very basic sense.

All breathing mods will affect the VE in some way, which wil peak typically at mid revs, and drop either side significantly. This is how most engines will be setup for the majority of normal car owners.

Changes in thermal effieciency can be made by increased VE, increased turbulence, ignition advance, fuel, combustion chamber design and so on.

So it's these efficiencies that are affected by mods like cams, exhausts, inlet etc etc. On a turbo car, I'm pretty sure that the turbo limits the VE to less than 100% , where VE is defined normalised against boost pressure, so 100% VE at 2 atmospheres absolute boost would be 200% (as assumed in the formula quoted thus far).

The most effecient recirpocating engines are big slow diesel ones, as used on big ships, they can reach over 60% TE, where as auto petrol engines are around 30%.

enough rambling for now!

Paul
 

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Re: Re: Re: OK folks it is a long one.

Adam Wootten said:
AFAIK the only cars to break into the 6's over the 1/4 mile are big V8's...
There are infact two 2JZ-GTE powered cars that have run into the 6's at over 200mph. They are the Bullish racing Solara's.

HKS's RB26DETT powered 180SX tube frame car almost made it as well (a 7.1 @ 196mph I believe) but couldn't get the traction - it had the power - the chassis is what let it down.

I find the fact that they did it much more impressive than some old school V8 that has just re-hashed the same old formula over and over again.

In short, smaller displacement motors are quite capable of making the requisite power levels to push 6 second quarters - it is easy to just re-hash the same old technology that people have been doing for years, but some of us prefer to push the boundaries and use new tech - as if you don't push it, you won't find its limits, and you get 0 progress.

Mario.
 

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Syed, efficiency palys a part in this, the theoretical ideal is a chamber size somewhere between 380 and 450cc smaller than that and the revs have to be very high up and torque goes up that way also so not a nice motor to drive.

The 1JZ and the RB25/26 were designed around this theoretical ideal.

Getting 100bhp/ltr is quite easy for cars with small cylinder displacement but try getting 800hp from an 8ltr V8, the efficiency drops off quite remarkably as that displacement heads to a litre per cylinder, put simply I believe David Vizard [probably the closest any man I know that deserves the title Guru] says that the same 'work' on a 1 ltr/cyl motor that releases 100hp/ltr on smaller displacement motors will return you 88hp!

Mathematically, he is spot on.
 

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Sorry I thought the thread title meant we were talking about power per ltr not just Cubic inches:D

Additionally I may have mis-understood this bit posted by your good self;

#Yes, but if you apply the same technology to the big displament engines, you'll get even better results!#

I was correcting you in that the 'same effort' with larger displacement you'll get worse results, just as David Vizard has pointed out, I only did the Maths afterwards to see if he was right.

My mistake.
 

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this post isnt exactly the best post in the thread i know, although its related to RB26's max bhp, and some of you will prbably flame me for it BUT, i remember reading somewhere in relation to the "R35" that Nissan had tested the RB26 and pushed it and found its absolute limit was about 1600bhp before it grenades itself (and that they were looking for a 2400bhp limit on the new GT-R engine).

Like i say this could well be untrue, but ive often been told i have a photographic memory, and i have a picture in my head of a page with all this information on including some rubbish about the GTR drivetrain and a Nissan Stagea. I have no idea where its from, i just know ive seen it somehwhere.
 

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"they were looking for a 2400bhp limit on the new GT-R engine"

Bit ambitious I'd say. Could your memory have been Photoshopped?

Phil
 

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I also have just picked up on this fascinating thread.

Must agree with Mycroft about optimum cylinder size. As someone mentioned earlier it would probably be better to increase bore rather than stroke, but an increased bore means more flame travel and probable combustion problems in the shorter available time with a high RPM engine.

The best way to have large piston area and short stroke is to have many smaller cylinders, rather than a few larger cylinders for a given capacity.

Another thing that fascinates me is that power seems to be more closely tied to airflow rather than engine capacity. As someone else has already pointed out, increasing the capacity alone is not going to make you any more power if the maximum airflow stays the same.

Now airflow is not going to be proportional to boost pressure, far from it. Double the boost (absolute) might increase airflow x 1.414 times or something, so there must be a practical limit to how far you can go with just increasing boost to gain more airflow. More boost is also going to reqire more power to drive the compressor, which must come from somewhere.

So jacking up the boost will be an exercise in diminishing returns.

No one has so far mentioned the effects of exhaust gas back pressure on power production either. A larger exhaust turbine is certainly going to better, but it will kill the engine flexibility.

If you could keep increasing the power to infinity, and the usable RPM range narrows to zero, what effect would this have on the performance of a practical road going vehicle ?
 
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