GoRideSno

I dropped by the Prototype Engineering shop today to ask the guy (can"t think of his name) if he was the one that turboed your car. He said he had talked to you. Shows that it's a small world after all. Did you get any good new information? I talked to him for a while but mainly about my projects, and his Lotus stuff. He had some pretty interesting things to say. He said that at BAE he helped put 80 turbo kits on the shelf and many 1 offs too.
Andy K

SilverSFR

GoRideSno,

I was able to talk to him. Fill me in on all of the information he talked about. Thanks for your help in locating him. The 928 is running perfectly. Well perfect enough.....

Thanks.

SilverSFR

Lagavulin

Is there any chance that you'll dyno it?

SilverSFR

Not much of a chance, sorry Lagavulin. My ass0meter dyno does tell me at full boost (+- 7psi) @ 80 hp is what I'm getting. Is their a formula that you can get an educated guess with? Last weekend I finally got around to replacing my cracked and leaking coolant reservoir. The information at Http://www.nichols.nu/tip796.htm was a great help. Not a hard job but smaller hands would have been helpful. This weekend I will be replacing a leaky oil line between the oil pump and the turbo.

SilverSFR

Lagavulin

This one will get us in the ballpark, but the actual number will be lower since we are not taking into consideration the density ratio, etc.

New HP = (NA crank hp) x (Pressure Ratio (PR))

First we calculate the PR:

PR = (14.7psi + boost) / 14.7psi
PR = (14.7psi + 7 psi) / 14.7psi = 1.48

This means the engine is ingesting nearly half an atmosphere (..with corresponding amount of fuel) more than NA.

Now all we do is multiply the PR by the NA hp, whatever that may be. In this case we'll just use the factory specified 220 crank hp:

New hp = (220 crank hp) x (1.48 PR) = 326 crank hp

Just for comparison sake, I just did the calcs on my spreadsheet which takes into account the density ratio, etc, etc.

Using 220 crank hp, 9.0:1 cr, 7 psi, no intercooler:
298 crank hp
1174 combustion chamber temp

The combustion chamber temp is pretty high if indeed there is no inter/after cooler (..and the cr is 9.0:1). Just curious, have you ever had a compression test and/or a leak-down test done on the engine?

SilverSFR

Lagavulin,

I have not done a compression test and/or a leak-down test . The 928 has been a sunday driver and under those conditions i have not come accross detination problems. When BAE installed the turbo kit they also installed a water injection system. I currently have the system apart trying to find parts to rebuild the pump and water bottle. the 298 crank hp does not sound that far off. the boost is controled buy a wastegate. if needed, i could run the boost out to @ 9psi. If i do this detination could be a problem.

SilverSFR

Lagavulin

Well, it's good to know that you have some sort of charge cooling mechanism in place; evidently it works too since you've been driving the car for a while.

If you can't find parts for the rebuild, you could consider installing an aftercooler which is a more robust solution than what you have now for charge cooling. You could then easily turn your wastegate up to 9 psi with no problem detonation-wise.

220 crank hp, 9 psi, 9.0:1 cr, 85% IC Efficiency:
365 crank hp
1047 combustion chamber temp

That's a nice jump in power. Also notice how the combustion chamber temp dropped too, way below Corky Bell's 'magic number' of 1075.

Of course, the calcs assume 220 crank hp. Keep in mind that if an inefficiency is introduced to the engine causing a lower NA hp reading (..such as an exhaust manifold that's not as efficient), the boosted hp numbers will be lower than stated too.

SilverSFR

Lagavulin,

What is an aftercooler, and what does it do. I would love to update some of the features of this turbo kit.

SilverSFR

bcdavis

Look!

You and John could have saved so much time and hassle!

Turbo "Simulator"

Ed Taylor

You have got to be kidding.

SilverSFR

Funny man you are bcdavis.

SilverSFR

bcdavis

That's right up there with the NOS subwoofer tubes....

http://www.crutchfield.com/S-uFfwa8t....asp?i=204NOS8

GoRideSno

SSFR,
Jim(?) told me that he did not install the water injection on your car. He seems to be a fan of water injection though.

I have a complete Varajecton I and a complete Varajection II. Neither has ever been installed. If you want one I'll give them to you for what I paid, $90. I would suggest an Aquamist system though.

Jim(?) seemed to think that your car could handle a discharge temp of 350 degrees without any form of aftercooling. He added that cooler was better but 350 was safe.

Andy k

SilverSFR

GoRideSno,
I just assumed that the Varajection unite was installed by BAE. I have very few service records for the first few years the car was built.
I would be very interested in your complete varajection ll. Tell me more about the Aquamist system. and how it works. Can someone please tell me what a aftercooler is?.

SilverSFR

GoRideSno

Aftercooler refers to a heat exchanger that cools the compressed air from the turbo or supercharger. Aftercooler and intercooler are generally used as interchangable terms. Aftercooler is the proper term if it is simply after the compressor. Intercooler properly refers to heat exchanger that is placed between 2 compressors.

The water injection unit serves the same purpose as the aftercooler. A proper aftercooler is superior. It is more reliable and delivers a denser charge since water molecules are not displacing air molecules.

The Aquamist water/alcohol injection system is the best unit available. It uses a special pump and a special misting nozel. Some cars in Europe come from the factory with it. I have seen them new on E-Bay for about $400 from various distributors. The E-Bay sellers have links to the Aquamist site.

HTH
Andy K