2lt 8v Turbo

[Quigs 1]

Hi all.

Just wondering what cam i can use in my 2lt turbo??

 

Can you use the 1.9 gti cam??

 

Quigs

[Mikey S 29 1 Cars]

Hi all.

Just wondering what cam i can use in my 2lt turbo??

 

Can you use the 1.9 gti cam??

 

Quigs

 

there was a discussion on this not so long ago. the dkz catalysed gti lump (122bhp) cam is the one to go for apparently. the standard gti cam has too much overlap for a turbo engine. it would just blow boost down the exhaust ports.

[Mikey S 29 1 Cars]

http://forum.205gtidrivers.com/index.php?s...mp;hl=turbo+cam

[whizzer71 0]

Hi I did a bit of investigation a while ago on the subject of maximising power output on this engine.

 

 

http://forum.205gtidrivers.com/index.php?s...mp;hl=whizzer71

 

Hope this helps !

 

Tris

 

[Jakob 1]

...the standard gti cam has too much overlap for a turbo engine. it would just blow boost down the exhaust ports.

 

No, remember when we have a disadvantage, the exhaust gas will blow back in the combustion chamber giving us limited access to reach MBT (minimal advance for best tourge) when tuning our ignition table because of early detonation. But it depents on the setup. Big overlap dosnt have to be an disadvantage.... Blowing through should be seen more as an advantage, as when it happens it cools the valves You will blow through on a supercharged engine and back on a turbocharged - general speaking

[petert 554]

But that's all a function of how much boost you can run, and thus how much you can afford to loose on overlap, which of course is all governed by the piston quality. I'd suggest that on cast pistons, with small boost, you'd want a cam with wide lobe centres, to maximise what boost you have.

[Henry Yorke 269 3 Cars]

I'd suggest that on cast pistons, with small boost, you'd want a cam with wide lobe centres, to maximise what boost you have.

Like the DFZ (XU9J1/AZ 105 bhp) cam?

[petert 554]

Like the DFZ (XU9J1/AZ 105 bhp) cam?

 

Ideal. More lift would be better, as these are only 0.405", but cheaper than a custom grind.

[tom_m 0]

But that's all a function of how much boost you can run, and thus how much you can afford to loose on overlap, which of course is all governed by the piston quality. I'd suggest that on cast pistons, with small boost, you'd want a cam with wide lobe centres, to maximise what boost you have.

 

using that logic you might as well stick with the standard cam then?

[Jakob 1]

Choosing cam overlap is among others a matter of analysing your flow setup. Not pistons or chosing pistons based on cam (not looking at possible clearence issues)... forced piston only restand your detonation for some more hours. If you have build a prober setup with good long runners on the turbomanifold, and big turbine you will have less back pressure and be able to run more overlab and boost. It is all a matter of getting the boost vs. backpressure near 1:1. High output engines run close to 1:1 (or even under). Low output engines is like the typical standard chip tuned XU 8v turbo engine with stock manifold and turbo running 1,2 boost delivering "boost-compared-disapointing" ~190-210 hp. Why, cause among others ignition and mixture are set so terrible to cope with detonation that MBT/hp is the loosing part. But the owner is still happy cause the gauge says 1,2 bar boost (hot expanded air). OEM the engine is equiped with a small overlab in order to fit in with the setup for delivering the low rev/high tourge famely car. When increasing the boost on such an engine/setup everything is wrong if we want high hp output (No flow + boost = backpressure = early detonation = retarding ignition + flushing cylinder walls with fuel for cooling) and retarding the ignition too much in order to cope with detonation can cause high exhaust temperatures and then it is the "spiral of detonation" that is getting turboed - not the engine, leaving us with a dangerious risch of pre-ignition.

 

Why do we see same engine deliver much more power on much less boost....because of a proper flow build up (manifold, turbo) Choosing cam in this case is not limitied on the backpressure/detonation issue, but now dimentioned for best possible flow. So if you have a bad setup (manifold/turbine) generating much backpressure go for the cam with less overlab to avoid the detonation issue. If you have a good manifold and huge turbine for high output, you have the possibility to include the cam in the flow build up and get high rev output.

 

Anyone have the figures on the DKZ cam to compare with ones from the aftermarked turbo-cam suppliers?

[Jesper Cronelid 0]

Jakob: Thanks for that lesson!!!! :thumbup:

[Henry Yorke 269 3 Cars]

Ideal. More lift would be better, as these are only 0.405", but cheaper than a custom grind.

Good job I had one as standard then! It has tiddly little valves though, but a nice easy way of lowering compression

[Bally 4]

SO for my Mi16 its std cams then or the PT1601

[sonofsam 5]

Choosing cam overlap is among others a matter of analysing your flow setup. Not pistons or chosing pistons based on cam (not looking at possible clearence issues)... forced piston only restand your detonation for some more hours. If you have build a prober setup with good long runners on the turbomanifold, and big turbine you will have less back pressure and be able to run more overlab and boost. It is all a matter of getting the boost vs. backpressure near 1:1. High output engines run close to 1:1 (or even under). Low output engines is like the typical standard chip tuned XU 8v turbo engine with stock manifold and turbo running 1,2 boost delivering "boost-compared-disapointing" ~190-210 hp. Why, cause among others ignition and mixture are set so terrible to cope with detonation that MBT/hp is the loosing part. But the owner is still happy cause the gauge says 1,2 bar boost (hot expanded air). OEM the engine is equiped with a small overlab in order to fit in with the setup for delivering the low rev/high tourge famely car. When increasing the boost on such an engine/setup everything is wrong if we want high hp output (No flow + boost = backpressure = early detonation = retarding ignition + flushing cylinder walls with fuel for cooling) and retarding the ignition too much in order to cope with detonation can cause high exhaust temperatures and then it is the "spiral of detonation" that is getting turboed - not the engine, leaving us with a dangerious risch of pre-ignition.

 

Why do we see same engine deliver much more power on much less boost....because of a proper flow build up (manifold, turbo) Choosing cam in this case is not limitied on the backpressure/detonation issue, but now dimentioned for best possible flow. So if you have a bad setup (manifold/turbine) generating much backpressure go for the cam with less overlab to avoid the detonation issue. If you have a good manifold and huge turbine for high output, you have the possibility to include the cam in the flow build up and get high rev output.

 

Anyone have the figures on the DKZ cam to compare with ones from the aftermarked turbo-cam suppliers?

 

Yes, on page 3 of this Topic Hilgie posted a table with DKZ cam info on.

[petert 554]

SO for my Mi16 its std cams then or the PT1601

 

If you've already got them, I'd use the PT1601 inlet and std. exhaust cams, with #2 pulleys on each.

[Bally 4]

Yes I have them and #2 pulleys. So I am good then