Porsche Enthusiasts Club Forum

What's your definition of "decent power" and "an absolute fortune" ?

Well for me, 300+bhp I'd call decent, but then I've never driven anything with much more than that!!

As for costs, well, I'm a diyer through and through, so like to spend as little as possible, but I'm talkinf about the cost of bolt on parts with a standard bottom end vs a fully forged, balanced, lightened bottom end that might jave cost £k's.

Nick mentioned £10k on an engine, but for a road or even track car that sounds like crazy money, more like race engine money!!

300 BHP is less than £1k if you're starting with a 250 bhp car, and AFAIK all the engines have forged cranks and pistons.

Yeah, I realise 300bhp from either Turbo car is not too much hassle, but Nick was implying that even 400bhp was achievable with a standard bottom end - so why not go for the same kind of build but use the 16v head and see where the gains are (or are not) made.

As I say, will be a good project

It’s true that the larger bore motors are less rev friendly. There’s quite a few of us who run 3L 8v motors which seem to hit a bit of a wall at 6000rpm. Nice flat torque curve which in effect still makes the car very quick, but just not quite as revvy if that’s what you want. If I was building another race motor I would consider a smaller bore (possibly longer throw) to cater for more rpms. My old almost stock 2.5L still made power up to just over 7000rpm whereas this larger bore motor just starts nosing off at 6k. The differences are 360whp to 505whp on the same dyno using the same fuel and boost. My friend Sean Buchanan has been running a turbocharged s2 motor (with aftermarket rods/pistons) with standard wet sump and on slicks for a couple of seasons. It is a daily driven road car but he runs it on the track to great effect. Go onto Youtube and look under Buchanan Automotive for his videos. My point being, this would be a cheap way of making a motor that you describe. It would have 500bhp +/- and he runs it at 1.5 bar with E85. You only have to find or build an intake and modify the headers to suit. He runs it off Vitesse Software, again a pretty affordable option if you don’t want to go to a full standalone setup. Even though Vitesse parts aren’t super cheap but the ease and simplicity presents a pretty strong argument.

Another secondary issue with the 8v heads is that you can’t fit a large enough Intake valve in there to compensate for the VE needed to push the air through much beyond 6000rpm with any positive benefit. I have 49mm valves in my head vs 45 or 46mm (?) stock size. I doubt you could fit anything larger in there and yet I’ve been discussing this with an Ex Ford Engineer who is very confident that this is why my motor is dropping off after 6k. The 16v head is also more resistant to knock. There are some that say not to run with Vario-cam while others have had success…if you’re looking at 968 heads.

I assume your running full slicks, not much rear camber ect?

Because if not, i would be surprised if you get round the track much faster than a well driven 330hp car.
On the road i find grip an issue with even my low power, the rear wheels (265 tyres) are lit up leaving a bend in 3rd on a dry road, id expect another 150hp to make it a major handfull and not much faster laps.
Obviously modern turbos with nicer spool will help but, as they say - power is nothing without controll..

Also, its a cheap job to get 320-330 and lots of torque from a 944T engine and they go very well in this state of tune, but thats where i would stop with a 944 engine, because beyond that is major expense for little gain compared with tuning other engines. You mention fitting the 2.2 Audi? If you want silly power- do that, a much cheaper route to 500-600hp.
It wont wreck its crank and doesnt have delicate bores either. (i think i mentioned it bolts to a 924 housing)
Oh and the noise...
Its a bit heavy and will move the weight forward tho.

The old 2.2L 5 cyl Audi engine is IMO not a better choice than a 3.0 8V engine.
Friend of mine had one built for his 944 S2 and while it makes a peak of 480 hp the car is still pretty much gutless off boost, which is the (only?) problem with this engine. They can be built to 2.7L but by that point they get pricey as well.

Yes, building a 3.0 right from the start is expensive, but when done right it will walk over some way more expensive cars, and this is the point.

Sounds ideal for a road car, might buy some more parts .

Sean has been running slicks on the track and keeping up or beating GT2's GT3's and other assorted Porsches. I've been running on Yokohama AO50 R spec as we were in an event down here called World Time Attack and that was the control tyre. We were running times equivalent to a 996 Cup Car on slicks. In the next event which was a Porsche Club Supersprint we took fastest time of the day and that was against a highly modified 996 RSR with a factory 4Ltr motor, a warmed and lightened GT2, a 962 replica and other cars...again, all on slicks while we were on R spec rubber. Our car is running a fair bit of Aero as well.

As far as only building the 944 motor to 330bhp, that's being a little conservative. Of course other powerplants offer many other options but you still have to buy that motor, modify it and fit it into the car. You could spend that amount on the original motor and achieve decent power. It's true that you may need to look at other components of the car but that would be the same with any motor. Suspension and brakes need revising for sure but you can modify the car to put that power down without slipping and sliding all over the shop.

We have had 417BHP and 398 ft-lbs of torque from a standard 100k mile 2.5 8v 944 turbo engine, without crazy custom mods, just the off the shelf parts we make or sell.

I think it made full boost at 3500 rpm, where it also made peak torque, and it made the 417BHP at about 5200 where it trailed off a little due to being on a standard intake manifold, throttle body and cam.

No mystery with 16v heads, we tested them and found we could make a little extra torque, which we already make too much of when we want to anyway, and they only start to give BHP improvements once you go beyond the RPM abilities of the standard oil system... A dry sump 16v engine would provide gains, especially if you went with some options to improve the RPM ability of the valvetrain as well as the oil system.

Has Nigel got this cab back on the road yet ?

What turbo was used?

Jon, how are you calculating bhp? Assuming this was on a car, not engine dyno? What % are you using to extrapolate from whp to bhp? I have heard/read many variations on this % for drivetrain loss.
Some as low as 10%, right up to 32%. I tend to use 15% just as a reasonable approximation.

Those particular figures for that car were using the basis of 20% transmission loss, with the dyno dynamics rolling road calculating (some would say estimating) the flywheel figure.

Many dyno operators go on the basis of 15 to 16% transmission loss for front wheel drive cars, and 17 to 18% on conventional rear wheel drive cars.

We always tend to test and quote figures with a 20% transmission loss for a few reasons.

One being that this is what we found years ago to correct for the difference between what we found on a 944 turbo engine on a SuperFlow engine dyno compared to the same engine when installed into a car and used on a DynoDynamics rolling road.

Another reason is to ensure that our dyno figures we give to customers are always less than they will find if their car is put onto another rolling road. If they put their car onto a DynoDynamics rolling road, the operator will almost certainly use the standard manual advice of using a figure of 18%, so the customer will get a higher reading there.. and as other Dyno's seem to read higher than a DD rolling road, if the customer puts the car on a Maha or other dyno, they are likely again to see a higher figure.

A customer is never unhappy if they put their car on another dyno and get more power.. But them getting less power is bad for public relations!

The last reason is that the 17-18% is based on a modern rear wheel drive car which is likely to be running less viscous oil than used on a 944, so a higher loss could be a good idea to compensate for this.

Rolling roads always are a comprimise, 9M commented once that they found that increasing airflow under a car during dyno testing not only improved dyno readings, but also made them more consistant run after run, which goes a long way to say how important it is to compare apples to apples, rather than to oranges, as just the positioning of the fans, as well as the professionalism of the operator can make a massive difference to dyno figures.

I at the moment am considering which dyno to buy, and one I have my eye on is one of the new MAHA dyno's simply because it seems to be the most accurate at calculating drivetrain loss based on a number of figures including a "clutch in" spin down after each power run.. which is not unique to MAHA, but it seems they have put a lot of effort into this side of the dyno.. and if a Dyno is good enough for the Porsche factory, Audi, RUF, Brabus, AMG etc, its good enough for me.

For an engine dyno, as with a flow bench, you cant beat a superflow, even a 20 year old one, as they seemed to perfect them long ago.

Terra, it was one of ours, a double ceramic ball bearing Garrett centre section custom made to mount onto the standard mount, Garrett turbine, compressor and cold side housing, but with a KKK #8 hotside re-machined to make it an equivalent #10 and to match the Garrett exhaust turbine.

Not cheap at about £1500 but the parts to make it were seriously expensive too.. We have used this turbo spec on about 5 or 6 cars now and every one has made similar figures on the dyno with similar parts, and some of them have clocked up some quite high mileages now without issues... Which they should do, considering all the parts are quality items, unlike some of the turbo's you can buy which use cheap Chinese or Mexican parts.