Skunk Workz

Vidar Strand's BMW E34 M5 3.8-litre Turbo has dyno'ed 1129 hp/1130 Nm at the flywheel...

Skunk Workz

Cast iron is crap. Stainless retain heat more than twice as well as cast iron.

"The right tuning and pressure"? With the right tuning and pressure a 951 could push that...given that the cylinder wall doesn't crack open or the gasket blows...

tammons

Does anybody else think that running 30psi of boost at 8300 rpm on 96 octane fuel, sounds like a bomb ???

Theoretically they probably could get close to 800-1000 on race gas if everything was perfect and it did not throw a rod. I have not seen any 3L 951's even close to that mark though. I think I remember the latest 968 turbo cup cars were making someting like 750 hp, but I am not sure about that.

As far as 1000 hp from an S4, I dont see where it would be a big deal. The crank is forged and the bottom of the engine is like an indy car engine. The weak point would be the rods and pistons and maybe valve float, but with the right upgrades like carrello rods i dont see whay not.

There is a guy down here that drag races a 5.4L 4v TT mustang and he is making over 1200 hp on race gas. All he did to his stock forged crank engine is replace the rods, pistons and the oil gear.

chris0626

Well I beg to differ... cast iron retains heat very well and is extremely durable. To my knowledge there are no manufacturer-equipped, turbocharged cars with stainless manifolds as they are extremely prone to cracking.

Perhaps I should have expanded this thought further... an EMS to finely control the A/F ratio and ignition timing. Something more advanced than just tossing in bigger injectors and an AFPR (although those 2 items will be needed as well).

Depending on the size turbo he goes with, will dictate the pressure he has to run. As I have read in a number of his posts, ultimate numbers are not what he's after, but rather a very streetable (albeit extremely fast) car.

And yes, a 951 can run that much with enough boost... my 2.0l can too, so what's your point? I'm sure he will not have to run a crazy amount of boost to get where he'd like to be.

chris0626

Yes, that motor is a giant explosion just waiting to happen. 1 touch of detonation is all its gonna take.

blau928

Um Chaps,

There's this little car that runs on pump gas only 2 Liters, turbocharged and makes 1000 Hp... Why is it so unfathomable...? (BTW, it's a reace prepped Ford RS200)

Now, I did not say how prepped the engine was.. More air makes power, not more pressure..

A 928 at 1000hp is not as easy as it seems. The block would need prepping to the likes of Sterling's block. Sorry Tammons, it (a 928 engine) is no way near the spec of an Indy Car engine. 1000hp is also not that easy.

And, for the record, those headers in those turbo Indy cars are an Inconel, Steel alloy, not Cast Iron... Very Very Pricey...! (For weight, not durability etc..)

The pressure (30PSI) is irrelevant unless you know how much MASS (kg's or #'s of air) you are moving, and the charge density after cooling... PSI is "RESISTANCE TO FLOW" nothing more or less.

Rods fail in tension, and are dictated by RPM, not HP as many would like you to think. Rods do not fail in Compression, Cranks do. Carrillo can confirm this..

2 cents

Lance J

thats true cause the roads r pushing vertically down on the crank. but our cranks r forged

Lance J

rods sorry

tammons

There was a shop down here that built a 928 S4 TT that made 950 hp and it held together. They explained to me what they did and it was not as much as you would think. In the end it does not really matter though, because the drivetrain comes apart a long time before you hit 1000 hp.

chris0626

No doubt about any of that at all... ultimate power can be had on just about any engine configuration, the question is how long will it last? And at what price? And how streetable will it be?

Herr-Kuhn

Tony,

I have posted GM results before and I have a dyno sheet on that car. 355 ft lbs and 265 HP...it was 100 degrees in the dyno room when I strapped it down. I'd expect another 30-40 HP with cooler temps, say 50-60 degrees. Quite small turbos in that car as well. The 355 ft-lbs came on at 3,300 RPM. Why do you call this chest beating? I have posted the HP and performance figures for that car several times now and it still stands as the quickest 4.5 liter 3-spd AT 928 out there. It was quicker than Carl's 5-spd car running the same boost in the 1/4 mile. I'm simply keeping interest in what is going on as of late...and at least I have actually built something, not just bolted something on that someone else built...there is a difference.

There is nothing wrong with Cast Iron. Stainless is over rated big time. The alpha is 1.5X that of stainless and it warps like an SOB under welding and with the thermal expansion/contraction. I'd take mild steel with thermal coating over stainless any day of the week...live and learn. I had to surface the Goldmembers 304 SS manifolds after welding because of the warpage. This was done with a very large table belt sander made for doing heads. I also believe log style manifolds can put down serious HP contrary to what people say about having to have a header. They last longer, offer less surface area for heat loss and are less likely to crack as compared to a thin, long tubular stainless design. It is a judgement call for sure....specifically with the 928s limited space. I've got some literature from 1971 showing a big block mopar with two of the crudest looking manifolds you ever saw and that car pushed out 1130 HP!

Richard is right on the rods...at least from a breaking standpoint...cracks always start in tension and the rod sees tension on the up stroke. More RPM, more tension on the rod. Too much boost can bend a rod, but I think this is pretty rare.

Why is it people still think that superchargers don't have a heating effect on the air? That is not true...the heating effect is caused by thermodynamic laws as well as the efficiency of the compressor. The turbo might impart a little more heat to the charge, but it is not significant like people make it sound. Some of the good turbos are like 76%+ efficient. You could take a 78% efficient turbo with a tight glowing red hot side and stand it next to a 70% efficient supercharger and still have cooler air. Then if you have an efficient intercooler you drop the temps back down and make more power. Good intercoolers remove heat without issue.

I also disagree that the 928 has plenty of mid range and top end, in fact I think that is where the car lacks serious punch. Not talkign about top speed, but rather 3,500 to redline.

Herr-Kuhn

Also...I'm not sure I buy the 1000 HP claims on that Bimmer. The intercooler appears to be of the size to support about 700 HP and the feed pipe to the throttle body is quite small in my opinion. I'll have more intercooler on the 928 then you see in that build. It might be possible, but seems a little high to me...nonetheless, that car is exceptionally fast...perhaps the ultimate sleeper? I know guys are pushing 600 HP out of the 2.2 liter Audi motors with about 38 psig and 8000 RPM...so it could be possible. 700 or 1000, who cares, it still demolished that 360 like it was a small economy car. You can hear the guy on the rev limiter in the Ferrari, and those cars are quite fast, so it puts things into persepctive. Mid range torque can do a lot for you.

DFWX

The pros and cons of supercharging versus turbocharging is not unknown.
Rootes superchargers have the advantage of nearly consistent levels of boost and air volume across the rpm range, which offers many advantages particularly at low to mid rpms and easier to manage air/fuel ratios etc. They also tend to respond rapidly (little lag). However, they require more horsepower from the engine to run, are more difficult to intercool and produce quite a bit of intake heat.
Turbochargers create boost and increase air volume at the square of engine rpm - meaning little to non at low rpms and then increasing boost geometric to rpms (actually to exhaust flow). Particularly if the motor is lower compression (thereby allowing higher boost), a turbo motor can be particularly lack luster in low to mid rpms. They also take time to spool up (turbo lag). However, a turbo tends to generate less intake heat and requires little horsepower (or power lose) from the motor. They generally have no effect (including no adverse effect) at lower rpms (driving speeds).
Centrifugal superchargers use a turbocharger compressor that is driven by a belt from the motor. They also generate increasing boost nearly square to the rpms, meaning little to no boost at low rpms and maximum boost at high rpms. Being belt driven, they can not make the rpms of an exhaust driven turbo, and therefore are less efficient and they require more horsepower from the motor than an exhaust driven centrifugal supercharger (turbocharger).
Superchargers also tax the motor by adding more weight-mass the motor has to move (turn), where a turbocharger is spun only by exhaust gas.
Because turbochargers make their boost at higher rpms, a turbocharger is superior to a supercharger for high levels of boost and air volume movement - even moreso in a street car.
A supercharged car may be more driveable in terms of smoother transitions of horsepower and in higher lower rpm horsepower and torque.
As the power limitations on the 928 appear to primarily be in the drivetrain and not the motor, it could be argued that it is nearly irrelevant what method of boosting is used assuming high enough octane fuel and/or low enough compression is involved, as power lose to driving the compressor could be offset then by a higher level of boost and air volume - given the 928 motor in any boosted form can make more horsepower than the drivetrain can withstand.
Due to the higher low end horsepower and torque of a supercharger set up, most would probably prefer a supercharger for their 928. While a rootes supercharger will make very consistent boosting, a centrifugal supercharger will least affect the motor at lower rpms - meaning also least affect gas mileages. If maximum horsepower is the goal, a turbocharger(s) is the choice.

In more pratical terms, a supercharger is generally superior for drag racing (as it is more simplistic to use in that application) and a turbocharger superior for road racing.

The higher the level of boost sought, the more superior turbocharging becomes, however. The horsepower demands of a mechanical supercharger increase substantially as the level of compression and air movement increases.

The challenges in turbocharging tend to be avoiding turbo lag, the balancing act between boost at mid rpms without having to wastegate and BOV too much boost at higher rpms (wasted energy),
and ducting issues concerning intercooling. If put inline, turbochargers (even off the shelf) could make 100 psi or more - although the intake heat would skyrocket. The more intercooling is used, the more turbo lag that will result and more psi lost to the intercooler and in-tube obsticles.

Did he ever load up any photos? What compression is the motor? To run 30 psi he better have low compression and very advanced intercooling - plus a host of fuel pump, air/fuel management, huge injectors etc or he is going to either melt his motor (running lean) or obliterate it (denotation).
I have no doubt that making 1000 horsepower out of a 928 motor is not a particular challenge, nor does it take 7,000 rpm to make it. Any 5 liter motor can make 1,000 horsepower via boosting.
The question is whether he has the $$ and understanding to do this in a way that does not near instantly destroy the motor and how will he address drivetrain limitations?
It is the latter issue that seems the more challenging and costly issue, not making 1,000 horsepower by radical boosting.
On my radical project motor (which is both turbocharged and supercharged (rootes), my primary focus is to increasing upper low through mid range horsepower and torque - rather that top
rpm peak horsepower. Inccreasing horsepower and torque at the bottom end of the rpm performance range does as much (if not more) to increasing both acceleration and road course performance than chasing the holy grail of top rpm peak horsepower - and is far less destructive
to components.

A couple of decades or more ago in my hod rod years of big block American V8s, I finally came to understand that for a street car it makes far, far more sense to target mid rpm torque and horsepower in performance goals and forget about trying to get 2 stroke radically high rpm horsepower. The latter is extremely costly, makes for a very unreliable motor, is highly destructive of components and ultimately resulted in a slower car.

With such limitations, it would be more desirable to have boost (psi and relative air volume) highest at the bottom of the performance rpm range and then boosting falling off as rpms increased - allowing the motor to make the greatest horsepower possible within the structural limitations of the motor and drivetrain.

Twin turbo and twin rootes supercharged 928s are rare, but have been made. They make a lot of horsepower. Any motor of this displacement would. However, once radically high boost is used, nearly all other components of the motor and drivetrain also then need modification and upgrading.

Dyno numbers are not really necessary to know the distinctions between supercharged (rootes or centrifugal) and turbocharged motors.

There are some rare, really cool blown and turbocharged 928s out there (parked in zillionaire's garages), so it unlikely his is the greatest. Then again, it may well be. I hope so.

DFWX

I can think of few things that would make more sense than a variable speed/drive on a supercharger AND dual fuel tanks (switchable) on a street performance car. On any boosted car I have owned, I always installed a smaller "performance" tank that could be switched between by a simple hardware store gas valve - the small tank for high octane fuel.
A variable speed drive (basically mini transmission) for a supercharger will give the best of both worlds. Driving around a 15+ psi supercharged V8 would be to drive from gas station to gas station, carrying a case of octane booster in the trunk. But if a person could have a choice between 3 psi and 92 octane fuel - or switch to 15 psi and 106 octane - they have a usable and very fast street car.

DFWX

All specs I read are the 928 rods are cast, not forged.