MAGK944

My technical explanation of why the 951 turbo is where it is. One of my na's has the airbox removed and a k&n at the AFM. When you look at the engine bay there is now a HUGE empty area behind the alternator where the LH engine mount is. I think the Porsche engineers took one look and declared "Zis is ver ve vill put ze turbo"

M758

Not really. The 968 Turbo was a homolgation special created for German ADAC racing series. In that series they wanted to race a 968. The rules at the time limited power/weight ratio so making big hp numbers would force them to add alot of weight. However torque numbers were not limited. So Porsche determined they coudl meet their target HP by using a 2V head on 3.0L block. This gave lots of torque, but due to less breathing not as much hp. However that was actually a good thing. So this engine was produced for raing and a few were make for street use so that the motor could be called a "production motor" The motor made less than 360hp even race trim.

So just like the original 944 NA motor it was designed to a power target and once achieve no further development was needed. The 911 motors have always been refined for ever increasing power levels as an extra 10-20 or more hp in 911 was always "good thing". Where as in 944 family once marketing derived power number was achieved no need to develop further.


As for the end of 944 family.... The main issue was the chassis was just old in early 90's. It was a 70's design that despite a number of refinements over the years needed a major refresh by 92. The 968 was mid life rework and the best that could be done a limited budget. Unfortunalty it became clear that despite the good things about 944 family it never captured the market appeal the why the 911 did. Same for the 928 which while a great car never could supplant the 911. So Porsche choose to phase out both the 928 and 944 family and concentrate on the next 911 as even that chassis was getting old too.

So in the 90's we saw the 968 as the entry level stop gap. Fresh enough to generat interest until the replacment came out. The 928 was given a bigger motor and make to last a few more years and the updates in the 964 we follow with new sheet metal to create the 993. All were ment to last long enough for Porsche to bring out the new cars. The 996 and boxster. Now the entry level car was special since it had mid mounted flat 6. Plust this allow alot of commonality between the 911 and boxster. So rather than 3 seperate platforms you had one basic platform with 2 variations. The hope was the boxster would share enoiugh of the 911 bits to accepted as the entry level car.

Best I can tell it worked and get this... The boxster was even cheaper than the 968 as well.

M758

Then the engine wont fit under the hood...

dirtyTurbo

My n/a motor sat so the cam housing was almost perpendicular to the ground for a minute or two when I was installing it into the car. It looked pretty sweet, actually being able to see the exhaust, but that would never fit haha

Raceboy

No R&D was necessary for turbocharged 16v 2.5liter because it actually was designed earlier than regular 8V turbo engine. Remember 924 GTP which had 2.5liter 16v turbo engine running 1bar and had 420 hp? It was the car that spent less time in pits of any car on 1981 (iirc) Le Mans 24h race and finished 7th overall.

On the topic, I turbocharged my 924 euro 2.0 and fabricated a crossover pipe to mount the turbo to the area where CIS stuff was earlier (converted the car to efi). It doesn't feel any worse but I don't know how the same turbo would spool on the right side. Boost treshold would be exactly the same, but maybe the lag (time between pushing the throttle and building boost) would be a bit less but its instant even now. People often confuse lag with boost treshold, dunno why.

But for my 2.5 16v turbo engine I will put the turbo to drivers side because of several reasons: 1. turbo is big (Holset HE341VE) and it is easier to find a place for it (actually the only place for this guy), 2. Since it is a VT turbo, split pulse doesn't apply, it doesn't have split pulse turbine housing but I plan to hold the 1&4 and 2&3 pulses separated by dual crossover pipe and join them right before turbo. This alone would compensate for transient response well enough or even improve compared to passenger side location.

Raceboy

It would fit with dry sump, as 9ff did it on their 16v twin-turbo.

80sriy

Thanks guys for your valuable insights.

Much appreciated : )

gux944

So I guess a muffler turbo solution is not a good idea or?

toddk911

Not needed. With the proper CAI especially in colder months, the intake manifold can be cool to luke warm even after heavy boost runs. The turbo placement is negated with proper sourcing of cold air for the charge air.

Can testify to this personally. In cold months I have done many back to back full boost hard runs and pull over pop the hood and intake is luke warm at most and IC pipe to TB is cool to the touch.

Reimu

I'd imagine the benefit of slightly faster spool would be offset from the added weight and bother of re-turboing a turbocharged car

David.N

Porsche did it right, Its more reliable, In the end the air entering the engine is still cooler then if it was on the exhaust side even if the turbo is under the intake manifold.

Who cares about boost taking a bit longer. Lag is awesome, and fun. When your on a track your always reving high so the lag doesnt even matter.

odurandina

the op sounds like a fun weekend project.

David.N

I am a mechanical engineer. I am not saying it is better then new technology, If you are an engineer then you should know that everything has to work together. In the case of the 951, it is just fine on the other side and was well designed to be on that side for a reason.

All cars have problems, Forums are going to be obviously only about these problems. These cars I have found to be very reliable. I know guys with 25 year old cars with half the mileage of mine (240,000) that struggle to stay on the road.

bonus12

What he said ^

However, I think there are many niche areas one can improve to gain more hp, but why this one? This one won't make a big difference for anything. There are other things one can do for the same amount of money, the same amount of work, or the same amount of ingenuity -- and gain more power.

Do you choose to modify the turbo setup just because you want to see if it can be done?

Emily750

The turbo design on this car is horrible. 5 feet of header piping = major lag. Turbos can take the abuse from heat. My Evo 8 turbo is the same size as the 61 in my 951 and has no lag.