bcdavis

Yeah... The spider is sweet.

I got mine because my idea was that a euro will be close to the same power as an s4, with headers, etc, and will not be an interference engine. Less complicated, etc... With CIS, no computer problems, etc... All mechanical... Lighter weight, etc...

But now, as time has gone on, I realize there is not much more I can do to boost my power, beyond a certain amount. But an s4 has a lot more performance options. Most of the aftermarket stuff is for the s4. And the supercharger kits put the s4 in a different league. The supercharger on an s2 only gets me about halfway there. Still fun, but if you want to go nuts, the s4 is the way to go, if you are into hot-rodding. And all the interior, electrics, etc, will be in better shape on a newer s4.

I don't regret my choice much either. And it's too late to go back!
I think I'm into this car for life, unless it gets totaled or something.
A bodykit and a supercharger, and I would be happy...
I've already replaced most of the parts in the car...

John.

What crap are you referring to? Like I said Tim should have good success with that setup.

I'm just not a fan of all these inertia dyno sheets floating around becasue I don't think they tell the whole picture, that is all I said, nothing more and nothing less. If you see this as crap, so be it.

A good boosted 16V 4.5 liter can perform vey well against a stock S4 and I too like the look of the old car better.

Jadz928

As far as the appeal of the 16v goes... it's Risky Business for me. Add what H-P and BC said... right on
As far as SC'ing an S2 goes... it's risky business as well. And I'm down with that.
Someday soon.
Great work Tim!

Weissach

This is great. Remember that most 16V cars are 5-speed and most S4s are automatic. This means it's easier and cheaper to make one of the early cars faster. What good is 400hp, if it's being wasted by an automatic?? I would think that potential S4 owners need to factor in a 5-speed conversion is speed is a priority.

hacker-pschorr

BC, I almost forgot one major advantage to the 16V cars. If you have a 5-speed, you already have the double disc clutch.

Lagavulin

First of all, your estimated hp numbers seem reasonable enough since 'The East Coast 928 Racers' with an otherwise stock 16v engine at 5.0L are running 300 and some change at the rear wheels. It will be interesting to see how much more the added displacement and cam will net you over that.

Ok, I'm curious. Let's try this and see what an increase in in 0.4 liters should net, using the above 16v 5.0L engines. First, let's find the hp/L using a manual tranny:

First, the crank hp:
300rwhp / .85 = 353 crank hp

Let's find the hp per liter:
353 crank hp / 5.0L = 71 crank hp/L

Alright, so those guys are putting out 71 hp/liter at the crank. Let's see what an additional 0.4 liters will net.

Applying hp/L to the Jim's engine at 5.4L:
71 hp/L x 5.4L = 383 crank hp

Finally, the rwhp using a manual:
383 crank hp x .85 = 326 rwhp

So according to these numbers which used the hp/L of the 5.0L engines at 300 rwhp, we see that an increase of displacement of 0.4L should yield 383 crank hp, which comes out to be 326 rwhp, which is not too far from Jim's estimate of 330 rwhp. Maybe those cams can produce another 20+ rwhp?

Back to the original question. As we all know by now, everything starts with the engine's NA hp, and let's assume a manual tranny to get the crank hp (..using Jim's original power estimates):

330rwhp / .85 = 394 crank hp
350rwhp / .85 = 412 crank hp

Now using a 85% IC and a centrifugal at 12 psi:

394 crank hp = 630 rwhp
412 crank hp = 659 rwhp

Yikes!

According to Corky, a supercharged engine consumes roughly .55 lbs/hr of fuel per supercharged hp. However, use whatever consumption number you think is best.

659 crank hp x .55 = 362.45
362.45 / 8 cylinders = 45 lb/hr/cylinder

Now if you want the number of the injector operating at a max of 80% duty cycle, then divide by .80 (..again, use whatever number you think is best).

45 lb/hr / .8 = 57 lb/hr injectors

Normy

OK Lag. A certain '85 S2 5 speed...probably 270 rwhp stock.

10.4/1 compression and 8 psi =

Normy-
'85 S2 5 Speed

Lagavulin

By the way, the numbers from yesterday will be slightly off as I didn't notice that volumetric efficiency and IC efficiency were transposed; sorry about that!

'Corrected' approximate numbers:

220 crank hp @ 8 psi = 297 rwhp
240 crank hp @ 8 psi = 324 rwhp
310 crank hp @ 8 psi = 419 rwhp


Ok, back to N!'s numbers.

First let's get the crank hp...
270rwhp / .85 = 318 NA crank hp

Using the above setup...
318 @ 8 psi = 430 rwhp

10.4 static cr @ 8 psi = 1087 combustion chamber temp, a little high according to Corky's 1075 'rule'.

mark kibort

Ok, what do i need to turn the holbert car into a forced air induction monster? starting at 330ish rear wheel, it would be nice to go to SpeedGT with 7-8 psi and run 440rear wheel hp. can it be done?? what is the cost. will it be race dependable too???
I think the speed GT guys would let me run a supercharger, as Im still running a 5 liter vs the VTS spec of 5.4 liters on the GTS. as long as the hp is less than Anderson, they wont have a problem.

now, I need to know costs!

you guys got me thinking!

MK

bcdavis

Cheaper than building a stroker.
And if you blow the engine, you get to keep all the supercharger parts you purchased,
and you can drop them back on top of another s4 engine from some mangled donor car, etc...

My point is that if you blow a stroked race engine, and have to rebuild it,
because of some catastrophic failure, it will cost you a lot to redo.

But swapping in a new, yet stock s4 engine, and adding the SC back on top,
should be a lot easier. And you could re-use any of the holbert goodies you
might want to keep... Cams, intake, exhaust, etc...

blau928

Mark,

It seems that with Murph's kit, and full Intercooling, you could run a bit more boost at the track, as you can use 100 octane which would allow about 12psi very safely and 500rwhp as Tim shows on his dyno charts..

The KB guys suggest Denso Iridium plugs, and I think the stock ignition will allow igniting the mixture at the 500 rwhp level with uprated injectors.. 36-42# hr.

The key to chamber temp control is density ratio mgt, and intercooler efficiency. In addition, exhaust will play a part, as it will lower the backpressure and allow better air flow through the motor..

I think Lag may agree, as (some of) our research comes from Corky Bell. Some of my other research shows that with boosted cars, the density ratio tied to intercooler efficiency is critical to maintain the 1075 deg chamber temp. If the system is designed with heat as the enemy, then detonation should be non existent...

Devil is in the details... I would have gone with Murph's kit if I wanted a centrifugal. I have chosen an Autorotor Twin Screw, which I intend to use in DE and some Open Road Events once I am done.. One item that Tim and I discussed when I spoke to him where I think you may want to seriously consider when running on the track is a bigger radiator.

I estimate that the additional heat will need to be extracted from the motor for continuous WOT Track situations..... My research has led me to get a 32in x 19 in x 5.5 in radiator. You may gasp at the additional weight, but I look at it as if NASCAR can get 800ehp all day long with 100 deg ambient CA desert, and still run cool, then good enough for me.

Another person who fully agreed on this principle is Hr. Buschmann from BRABUS (Mercedes Tuning) They boosted the 600SL to 650+ehp, and doubled the rad to be able to run all day long on the autobahn in Germany.

Well, Devil in the details, I am sure you know this being a racer and all that.. I will come out to Laguna in May to watch you guys..!

Cheers,

BC

Blau - who is doing the radiator for you?

bcdavis

GROUP BUY!

blau928

Brendan,

C&R did the engine Rad, it is a NASCAR unit, and is not a budget item. A new one costs over 1k. Call David at C&R, and he will happily build one for you. I have modified the tanks so it can fit in the 928. HM Marston Aerospace did the Intercooler rad, and it is from a Reynard race car.. Also modified to fit in the 928. I am unsure of the price of the HM unit, as I got it used. However, contact HM Marston in England, and I am sure they will sell you one. It is 24in x 13.5in x 2.5 in. I think it will also be 7-900 new.

For everyone's info. When I started this project, the design I arrived at for the 928 did not exist. I did most of the design myself, and had help from many engineers, and the Big 3 with parts or allowing me to take measurements to mount the parts. THANK YOU Mark A, Marc T, Susan T, Jeannie & Dave.

Up to now, it is all just theory, and my money spent on parts and engineering time, as the car is NOT yet finished. When complete I will post pics for all to see. However, this is my car, built how I want it to be built, and I really don't care if anyone approves or not. I am paying for it. I am not planning on selling any kit, and I am NOT doing this for a business. I have said this to all who have asked so far (you know who you are.)

I think think my design is way too expensive to offer as a kit, and even as a group buy. You could buy an S4 and have money left over for what I have spent on the parts alone. Again, my money, my idea, and my car. I am NOT, nor WILL NOT be asking ANY of YOU to buy ANY SC KIT FROM ME.

I apologize for venting on this thread, but I want to make it absolutely clear, as I have seen the threads and criticizms on this board, IMHO many times uncalled for. I will be happy to share information with any of you who want to ask, and for the betterment of the community.


Thank You All,

GoRideSno

Blau,
It was a pleasure talking to you again tonight.

Should anyone concern, Blau seems to have the calcs behind his theory.

He will soon have an extremely fast and powerful 928 S4.

Should anyone doubt his commitment to such, consider his time and money spent. His final price paid for his system will be beyond the price of an S4 with an intercooled supercharger installled.

Best of luck Blau and keep us informed.

Andy K