Turbo lag

Draco · Post by **Draco** » Fri Dec 04, 2009 7:29 am

Since I got the S13 it had alot of turbo lag, on the bottom revs the car is dead only starts pulling at about 3400-3500 revs....I have tried to increase and decrease the fueling and timing, decreasing the timing helped a bit but is still DEAD....maybe I am just use to my ZX....but that can't be, the ZX's are known for their lag.....wich isn't close to the SX.

Gary suggests that it is because of the forgies that are low compression.....I still need to check the compression but I doubt that it will be less than 800kpa(0.8 bar)....that was where my red SX was....and it had minimal lag with the T28....not close to what I have now.

So that leaves me to believe there is something else wrong.....the car is not tuned properly but I doubt the turbo lag will get better.

Suggestions?

Charlvdw · Post by **Charlvdw** » Fri Dec 04, 2009 7:59 am

What' your AR's?

Gary57 · Post by **Gary57** » Fri Dec 04, 2009 8:24 am

You have dished CP pistons so your CR is probably down at like 8:1. Remeber the CA wont have the same low down torque as your ZX.

Wes · Post by **Wes** » Fri Dec 04, 2009 8:36 am

My SX also used to feel like that. When I checked the error codes on the ECU it turned out that I had a busted knock sensor so the ecu was completely retarding the timing. After Gary fitted the dicktator for me the car problem was gone.

Is your SX running a std ecu?

Charlvdw · Post by **Charlvdw** » Fri Dec 04, 2009 8:48 am

Wes wrote:My SX also used to feel like that. When I checked the error codes on the ECU it turned out that I had a busted knock sensor so the ecu was completely retarding the timing. After Gary fitted the dicktator for me the car problem was gone.

Is your SX running a std ecu?

Hes not running the std ecu anymore.

Draco · Post by **Draco** » Fri Dec 04, 2009 12:40 pm

Wolf 3D.....

Gary the lowest those go is 8.5:1 which is presicely the same as the standard pistons....so I don't think compression is my problem.

Gary57 · Post by **Gary57** » Fri Dec 04, 2009 12:44 pm

Stock SX pistons are flat top, yours are dished so unless the piston goes above the block then you have a lower CR, simple really.

You have a lower CR that is why you have more lag...

Draco · Post by **Draco** » Fri Dec 04, 2009 12:55 pm

I get what you are saying Gary....but it is not that simple, even if a piston is dished or bridged, it is made for a certain compression.....these were made for 8.5:1 cpr.....am I wrong in saying that a piston made for 9.5:1 that is dished will not give you a cpr of 9.5:1 but 9:1...

Guy · Post by **Guy** » Fri Dec 04, 2009 1:17 pm

You're kinda wrong. In fact the whole idea of listing pistons as "x" compression ratio is wrong.

It'll only be that CR for one particular combination of stroke, bore, conrod length, head volume, and total combustion chamber volume.

Change any one of those things, even with the same "x:1" piston and the actual CR will change.

Only way to truly know what your CR is, is to measure or calculate it from measurements.

Gary57 · Post by **Gary57** » Fri Dec 04, 2009 1:57 pm

Yip, Guy is correct.

Guy the rest of the motor is stock though.

Draco those pistons are 8.5:1 they never were. Ask Barend, CP supplied him the wrong pistons the second time around and he didnt exchange them for the correct 8.5:1. Your pistons are 8:1...

Charlvdw · Post by **Charlvdw** » Fri Dec 04, 2009 2:14 pm

So will skimming(head/block) solve the problem?

Draco · Post by **Draco** » Fri Dec 04, 2009 3:25 pm

Interesting point there Charl....the head has also been skeemed alot....

This is what happens if your head and block has been skimmed to many times.... so I fixed it by grinding a bit of the waterpump

By the look of that my compression should be up....but ok, I think for me to rest on this issue I need to take the compression and work the formula to see what the cpr is.....

Draco · Post by **Draco** » Fri Dec 04, 2009 3:49 pm

I'm kinda screwed....I thaught I could work out the CR if I had the physical compression in the chamber that I measured with a tester.....

I need all sorts of things, how thick the HG is, what CC the combustion chamber is, the stroke I know and the piston size but not the chamber, it was bored bigger....deck hight.....I don't have all the answers...

Let me ask this....if the tester reads the same as my old compression....would that not mean it could spin the turbo up the same....?