Geoffrey

How are you doing the testing of the intercooler on your chassis dyno? I have not found that the chassis dyno provides a good indication of real world intake air temps. Usually the temps are all over the place since it is difficult to get the air to run through the intercooler and the engine also heat soaks.

"What one has to realize that when you install a larger compressor wheel on the same turbine wheel, the actual shaft speed slow down and actually reducing the exhaust backpressure."

How is this occuring? Backpressure is between the turbine and the exhaust valve. If you slow down the turbine wheel (shaft the compressor is bolted to) you effectively slow the exhaust flow and increase back pressure.

Kevin

Geoffrey why would you be slowing the exhaust flow down? If your wastegates are set at 1bar, the larger wheel will be generating the 1bar at a slower (shaft speed) RPM. The exhaust flow is going to be similar (out of the head) however as it passes through the turbine wheel which it must, the resistance is less at lower shaft RPMs vs at the higher shaft RPM's that is was previously turning when it had the smaller wheel.

Geoffrey

The engine is an air pump, if you are flowing more air into the engine as a larger compressor would because it is more efficient, then more air is exiting the exhaust port. You asserted that the larger compressor wheel would be slowing the turbine shaft or effectively the turbine wheel itself. The slower moving turbine shaft will not allow the exhaust to exit and therefore cause higher backpressure. The exhaust energy is being asked to move an effectively heavier object (turbine/compressor wheel assembly) and it will slow the velocity of the exhaust down. The exhaust velocity and mass is the engine that drives the turbocharger. If the turbocharger assembly is heavier, then it will need to do more work and that work is represented by backpressure.

Kevin

Geoffrey I said it is at a 1bar to 1bar even ratio between the different turbochargers. One having the same turbine wheel and smaller compressor wheel vs the same turbine wheel with a larger compressor wheel. Exhaust is also being dumped at a greater rate through the wastegate. The end result is that the rotating assy with the larger compressor wheel is working at a reduced speed and with more exhaust being dump out the gate and the lower shaft RPM, you do have less backpressure.

911/Q45

Let me see if a layman has this straight:small wheel=faster spool and higher rpm resulting in more backpressure due to a smaller space for the gas to pass through and increased friction from the faster wheel rpm. Big wheel=slower spool and rpm, but less backpressure due to bigger space and less friction. Anywhere close?

Rickard 993 Turbo

Is there any need for my to do this WG adjustment, stock k16 430hp kit...I also have a little dip in boost, i have the 0,8 bar late i think

Kevin

Rickard, you can adjust the "stock" K16's 2 clockwise turns to tighten up the actuator rod. Make sure that your roatations are marked and precise. I posted a article about this with the factory instructions a few years ago. One interesting thing is that many cores that have come from Europe have had adjustment of 3-4mm done on them. If you need pictures email me.

Rickard 993 Turbo

Thanks Kevin

Do you suggest me to this or should i leave it alone..?

I will search for you article about this, should be nice to read

When you say the Euro turbos has 3-4mm ,what do you mean then

thanks again

Kevin

In 1997 there was a Porsche tech article addressing low power or sluggish 993TT.. We aren't talking about gaining 15HP or power gains with a Motorsport 450 kit.. A 2mm adjustment added enough preload on the wastegate to keep the barn door shut longer in duration. This allow the turbine wheel to spin up faster and longer. It "could" net you a 10th of bar increase, however, the ECU will adjust it back to within factory parameters. This adjustment will help the mid RPM dip..

I can't tell you to do it or not? You can also measure where your actuator gates are set now and post the measurements with reference points as to how you got those measurements and I will tell you if they are stock or not..

Cores and turbochargers that have come across the pond have had adjustments done already.. It was "not" factory.. It was either done at the dealership or a tuning facility.. I must stress again that you must keep the rotation or adjustment in sync. If you lose it you will have to purchase a regulator and dial indicator to sync the actuators correctly.

Basal Skull

well, I did the adjustement - marked out exactly where the nuts were on either side of the adjustement arm (after taking off the little clip that spans the two nuts), screwed the more proximal nut in toward the 'Pot' then the more distal nut. 2 turns. I can't comment much on what I saw on my new to me mechanical boost guage - happens too quickly and I'm concentrating on driving the car. The dip is virtually if not completely gone, much smoother acceleration, according to my G-tech pro, the fastest 0-60 times I've had and most net horsepower I've recorded so far (with a passenger on board -the other runs I had done previously did not have a passenger!).....Thanx Kevin

Ryojo

ACEparts_com

I'm going to be right behind you tightening up my nuts!

Kevin

I promise that I will post the factory tech sheets soon!! Guys give me moments to do it though.. I have to scan it and then post it..

Rickard 993 Turbo

Please do...

I will take a picture as soon i have my car back, Ditec and sunblock on vindows are on the way..

ACEparts_com

Please post the pictures if you get a change

ACEparts_com

Update; did a search, did the measurements and found 34.30 and 33.95mm