Problem with 993 RS engine

[safe]

A friend of mine has a 993 RS with engine problems, it doesn't have any power on the top, which we got confirmation on by this:
Torque on the left, crank hp on the right. This engine should have at least 300, maybe 320 since it has better cams and headers.



Lambda:




We have tried a bunch of things:
*Checked cam timing.
*new airflow meter
*removed vario ram
*changed knock sensors
*changed coils
*changed ECU

All cylinders are the same, did 6 identical dyno runs with 1 injector disconnected at a time.

We think that it's an electrical problem and not a mechanical. But we are running out of ideas now...


Here is an older dyno run when the engine ran fine showing 302 crank hp.

[Trophy]

Did you check the ignition module (under drivers seat near ecu) Changing the coils won't show if the module is working properly or not. At idle pull the lead from one see if the idle changes at all, then try the other.

Is the Varioram working correctly? is there a vacuum leak at all?

Compression and leak down numbers, what are they?

Do you have a Bosch PST2? I would also check the following:

MAF
Air Temp sensor

Regards,

[safe]

Originally Posted by Trophy

Did you check the ignition module (under drivers seat near ecu) Changing the coils won't show if the module is working properly or not. At idle pull the lead from one see if the idle changes at all, then try the other.

Is the Varioram working correctly? is there a vacuum leak at all?

Compression and leak down numbers, what are they?

Do you have a Bosch PST2? I would also check the following:

MAF
Air Temp sensor

Regards,

We haven't checked the ignition modules, we ran it on one coil at a time, so both work. Maybe if one module is a little bad and don't work over 4500 rpm.

Varioram is working, also just tried it with it removed (working i high rpm mode).

Compression is good, don't have the numbers, equal over all cylinders. Haven't done a leak down. Engine had a top end rebuild recently after an over rev that bent a few valves.

PST2 is that the "hammer"?
Error codes was checked at the dealer, nothing.
MAF is new
Air temp sensor, I don't remember if we changed or not.

[rsscotty]

The dyno graph looks like it may be air flow limited. There are two places that the throttle cable can connect to on the throttle body. It has to go to the highest lever towards the center of the engine. The other one is only used if the car has cruise control.

[safe]

Originally Posted by rsscotty

The dyno graph looks like it may be air flow limited. There are two places that the throttle cable can connect to on the throttle body. It has to go to the highest lever towards the center of the engine. The other one is only used if the car has cruise control.

It gets full throttle, no doubt about that. The intake has been apart several times and checked.

The feeling you get is that the engine "wants to go" but is held back.

[Edelweiss]

Hi,

Next step to go is checking the exhaust side.

Is there a catalysator ?

If yes find out if it is flowing correctly.

What kind od header / silencer configuration are you running ?

My dyno can check torque / power / lambda / and the real ignition timing simultaniuously.

This could help in those cases a lot - talk to your dyno shop or simply find a dyno dynamics digital system in your region.

Best regards from Krautland

Dirk

[safe]

Originally Posted by Edelweiss

Hi,

Next step to go is checking the exhaust side.

Is there a catalysator ?

If yes find out if it is flowing correctly.

What kind od header / silencer configuration are you running ?

My dyno can check torque / power / lambda / and the real ignition timing simultaniuously.

This could help in those cases a lot - talk to your dyno shop or simply find a dyno dynamics digital system in your region.

Best regards from Krautland

Dirk

Yes, we thought about the cat, it had the original RS exhaust, so we changed it. It now has a complete system from a 993 RSR that we know works.

Yes, I agree that we need to know what happens to the ignition timing, haven't found a dyno yet around here that can.

[Lapkritis]

You should be able to data log through the obd port if you have one.

I use http://WWW.ross-tech.com as I bought it primarily for use on my daily driver audi. Pays for itself in no time as the dealer charges an hour of labor to pull codes. Used it on our dodge truck to trouble shoot a bad throttle position sensor that wouldn't throw a code. You might find the same just data logging while driving.

[safe]

Is it possible to log ignition timing through the ODB??
I think I can borrow a Duratec.

[Lapkritis]

Yes, you can with Rosstech vagcom as it interfaces with your laptop and saves to your computer hard drive. You can then view the data in an easy to read excel spreadsheet.

[geolab]

not on a 993 RS, no timing log
Moist probably ou have a vacuum problem as said before.
Remove the auxiliary blower on the left of engine, plastic all out.
Behind on top, you will notice there is a rubber vacuum hose coming from the left body panel.
It connects with a T connection with two legs. Like the Phi letter in greek.
It is from rubber, and three more vacuum hoses connect to this piece.
Grab it from middle and press it. If rubber is soft and you can press it, you should change this piece.
This piece becomes soft, and your vacuum varioram at 4500 rpm will not function if it is soft and clogs with high vacuum

[safe]

Originally Posted by geolab

not on a 993 RS, no timing log

I was afraid of that. To make it further complicated this is a club sport, which differs more than you would think from an normal RS. An ECU from a normal RS won't work, must be from another club sport.
For those who don't know, there was only 200 CS produced.... Luckily we could borrow an ECU from another CS in sweden.

Originally Posted by geolab

Moist probably ou have a vacuum problem as said before.
Remove the auxiliary blower on the left of engine, plastic all out.
Behind on top, you will notice there is a rubber vacuum hose coming from the left body panel.
It connects with a T connection with two legs. Like the Phi letter in greek.
It is from rubber, and three more vacuum hoses connect to this piece.
Grab it from middle and press it. If rubber is soft and you can press it, you should change this piece.
This piece becomes soft, and your vacuum varioram at 4500 rpm will not function if it is soft and clogs with high vacuum

I'll check the T connection, but it's not varioram related. In the dyno above the varioram was gutted completely to remove it from the equation.

[PFM]

Magnus,

Above you say the variorum was gutted completely, what do you mean? The controls were removed? As mentioned if the butter fly valves are in place they need controls. If not then ignition is my next guess,

[safe]

Originally Posted by PFM

Magnus,

Above you say the variorum was gutted completely, what do you mean? The controls were removed? As mentioned if the butter fly valves are in place they need controls. If not then ignition is my next guess,

Intake disassembled and inside all flaps removed.

[geolab]

Originally Posted by safe

Intake disassembled and inside all flaps removed.

there are two operational throttle bodies, the top one for low rpm, and the bottom one for high rpm. If you remove the flaps in the varioram, the trumpets would not open in the intake tubes, thus it is like air is limited to half gas pedal push.
You know that air intake is vacuum driven. the longer the intake tubes, the more air goes in and colder it is.

[safe]

Originally Posted by geolab

there are two operational throttle bodies, the top one for low rpm, and the bottom one for high rpm. If you remove the flaps in the varioram, the trumpets would not open in the intake tubes, thus it is like air is limited to half gas pedal push.
You know that air intake is vacuum driven. the longer the intake tubes, the more air goes in and colder it is.

The trumpets where also removed.
This is how it was raced when it was new, they did't believe in varioram.... The varioram was later put back in.

[Bill Verburg]

Mine was down 50hp at the top end because of a vacuum leak up under the dash board w/ a contribution by a failing check valve.

all of the vrams use the same vacuum controller for the fresh air flap in the dash area , the 2 vram actuators under the intake and the resonance flap, there are also 2 check valves on the tree on the left and several vacuum fittings that are prone to collapse