944 turbocharger options

[PSH]

ORIGINAL: 333pg333

I pretty much agree with TTM / Thom and given the chance, would build up a 16v motor. I think those that say the 16v turbos are breathless in lower rpm compared to 8v just haven't been in one. It's more the long runner intakes of the 8v that give them the early to mid range tq as most 16v turbos have aftermarket shorter runner intakes. My friend's 951 with a turbo'd S2 motor is very quick and he hasn't done anything stupidly custom on that motor. I would also possibly go down a little in capacity (for a race motor) if I was building another motor but for a street car, going up to 2.8 or 3+ltrs is a worthwhile move and not really expensive in the long run. Besides, changing the pistons and rods from 25+ year old stock parts is advisable anyway. So factor in a crank and you're there.
I think we squeezed about 330whp on a Dyno Dynamics dyno with my stock 2.5L motor with a GT30 and bigger cam. With some headwork it would have been a little better too.

Sorry must have missed your reply Pat... just to say that personally I am very acquainted to 16V engines although granted I haven't driven a 944T engine with 16 valves. However I have driven some very powerful 16v cars including my son's 500 bhp Cosworth and it's from these drives that I make my comparison. I like the feel of an 8V turbo charged engine, the power curve is more stable, better low end and I don't feel the need to floor it to release the power that the engine has. Although I modify my cars I try to keep the original feel to the car with just a little more go, ok a lot more go but the delivery and feel of the drive is what's important to me, I don't want to loose that 944T magic. I accept that these are my own personal views and not to everyone's taste. As I stated in the beginning, 16V is fine if you want to rag it all day on a race track but not so good for general road use, I am talking turbo's and I am talking modified engines here. yes you may get a little more from 16 valves but IMHO you loose more than you get. Porsche themselves used a 16 valve head for the Le Mans 944T's but an 8 valve for the road and as has been pointed out the same goes for the 968 turbo. With the mods that have been done to 944T engines over the years the engine has proved that it is capable of some serious power with 8 valves, 16 valves may gain a little more at top end which is why it's better for the track.
Having said this I accept that others have different views and respect them, each to their own as they say, enjoy your cars in whichever form they take, the 944T is a very special car...

Pete

 

[TTM]

Well... you can prefer 8V engines for the sake of it, but suggesting they might be superior to 16V engines because you like them better does not sound very objective to me.

I understand what you mean regarding mid range vs top end, but the fact is that a "correctly built" 944T 16V engine will have the same mid range as a "correctly built" 944T 8V engine. What might suggest the 16V may have less mid range is that power keeps climbing at upper rpm while it usually falls down on an 8V engine. When evaluating engine performance folks like us tend to pay attention to the rpm band during which the engine will accelerate the hardest, so we are always going to rave about the great mid range of an 8V engine since it will stop breathing past the RPM point which the 16V will begin to shine - even if the torque curves have the same shape and values until this particular RPM point.
For similar reason many people believe a 944 S2 has more grunt down low than a standard 944 turbo engine off boost, but if if you compare the charts in the owner's handbook, the 944T engine has actually more torque everywhere.

As for the original 968 turbo, please be aware that they were a patchwork of what was left at the factory back in these difficult early 90s, and having the chance to drive one on a regular basis, I can tell you they leave a lot to be desired in terms of outright performance. I was impressed when I first passengered in one ten years ago but the engine feels even more strangled in this car than we all know it originally feels in a 944 turbo, and it's not too difficult to build a 3L 8V car that will be much faster.

You make a good point about Cossies, but having never had the chance to see for myself how they performed, I might be tempted to think the relative lack of low end and mid range you suggest might be due to a small capacity of 2L coupled with generally oversized turbos...?

Anyway, different ways to skin a cat and all that

 

[333pg333]

Hi Pete

I have to again agree with Thom although preface that with all due respect. Not to say the 8v can't be made to achieve good results. (shameless plug https://www.youtube.com/channel/UC7gkao2axZSZRQRdyWld9oA) Plus I think that even a mildly modified 2.5L 8v with say 350bhp is a nice quick road car. It was far easier to use the 8v for the factory 968turbo as they had cost and power constraints anyway. Clearly not having to re tool was attractive as well. I'm sure whatever you come up with will provide plenty of satisfaction, and that's the bottom line! []