Race Engine Forum UK

I have a stock Croma turbo T3 turbocharger on my 2L 8V. Its ok for about 250HP maximum. My goal is to make around 300BHP or 200wkw without too much boost, maybe 18psi maximum.

I have a large turbo on my Uno, Its great for top end power and fast race tracks but its difficult on the street and for tight hillclimbs etc. I dont want that, I would prefer a better compromise between power and driveability. I was thinking something allong the lines of a 16V integrale turbo would be good. The turbo must be bolt on, i.e. a hybrid of the Croma turbo if you like. I have decided on these specs but im open to suggestions.

Stock T3 turbine with a backcut, 0.48 A/R
TO4 compressor wheel, about 50mm 0.6 T3 housing

Im not sure on the compressor wheel, maybe a TO4B similar to the 16V Integrale or something slightly larger, a TO4E something around a 50 trim.

Dear Steve,

I have a modified 16V, and converted from n/a to a turbocharger over-pressure induction and went through the exacting process of turbo selection very carefully for my street application. The aim was a solid and sustainable 300hp. My final engine specification and its development through much of GC …œextended correspondence course‚ and GC components reached this goal straight from the box easily at 1Bar. More being on tap but given I had machined the standard turbo cast pistons to a Cosworth profile (radius and reduced …œsquish‚ land area and also cut from the crown to reduce CR, I chose not to go further and just chase failure. I will be rebuilding with more solid internals now having proved the package. To cut to the short answer, my final turbo selection was Garrett T3 super 60 trim compressor, .48 A/R turbine housing with standard T3 turbine. Compressor map as below. In terms of driveability and response, spool time is minimal and very strong and the resultant spread of torque is excellent. I will upload the rolling road results as soon as I can convert the format. I considered the 50 trim, and 57 trims but these did not make a suitable match in my opinion, and I have not been disappointed by the results I obtained. However, if your aim is above the 320hp mark then this unit will not be suitable, it will not meet the required duty and mass-flow requirement with efficiency and without the generation of excessive heat ¢‚¬Å“ all is a compromise that has to be made carefully to your intended application, engine, drive-train etc which I¢ž¢m sure you know very well.

Thanks for the reply. I am very surprised with your choice. Its a decent downsize from a standard Integrale turbo. (I assume you have an Integrale).

I will reply to this in more detail later :)

I have finally received and fitted my turbo upgrade. Specifications are as followed

T3 0.48 A/R, backcut
TO4B V trim compressor in 0.6A/R front cover

I have only had a chance to take it for a quick drive tonight. Its still running the same boost, a solid 10psi.

My first impressions are good, Its very streetable, useable. There is virtually no more lag over the stock T3. It will still make 10psi by 3000rpm. Im quite surprised, I could probably benefet from a larger turbine, 0.63 housing or use an O trim shaft.

Power seems good but its not warp factor faster. It has noticeably filled in the top end as expected. The power delivery is much better. Comes on much softer which makes it better to drive. With the stock turbo all inappropriate broke loose at 3500rpm, then it would taper off. It now has less wheel spin and pulls better once it gets going. At 10psi its a win win upgrade as far as I can see, it should be standard.

I think more boost should make a massive difference too. I want to run around 15psi. I hope to have more information with comparable data soon.

I originally did not want to use this turbo as the compressor map suggested it would operate well in the surge zone (see map). Going off the compressor maps, I would have preferred a TO4E 46 or 50 trim. However my turbo engineer still wanted to use this one. The results speak for themselves. Theory can only go so far, experience counts for a lot.

Hi Steve,

I think he has an na engine..

''converted from n/a to a turbocharger''

I might be wrong though.

Tom

Right, I missed that. The engine could be in anything.