Replacement Octavia engine in Leon 1.9TDi short of low end pull

[Team-Joker]

Due to 'cheap' maintenance a new engine was needed in my early Mk 1 Leon TDi. The ECU had originally been chipped by Superchips to give 140bhp. New engine only gives 110 bhp but an unusual torque curve which is almost straight until 4,000rpm. Obviously the ferocious low end grunt is now missing. Superchips say chip still working as it should, local seat specialists spent ages on the problem with no luck. The new engine looks as if it is out of an Octavia. Despite the same engine codes it seems as if Skoda engines or later mods to that range of engine have caused this effect.

The car feel fine mechanically but need to be reved if strong acceleration is needed.

Has anyone got a solution which has foxed the experts?

Cheers

 

[glynnd]

Is the egr valve in good health.
Glynn

 

[Team-Joker]

Hi Glyn

How do I check the EGR please? What are the symptoms of a gummed up EGR?

Cheers

 

[Muttley]

Was it only the engine that was replaced, or was the gearbox swapped as well, as one big lump so to speak? Just thinking that the gear ratios might be different.

I presume the failed engine was also a TDI 110, ASV or similar? What's the new engine's code?

How do you know what the power values and torque curves are like - rolling road results? Can we see them?

From what you've said, I'm guessing that "almost straight until 4000rpm" means starting off low and rising in a straight line. If that's the case I'd say your turbo wasn't working properly, perhaps the vanes have jammed in the full-open position, or the actuator is jammed, or not connected.

Or maybe the turbo is different in Octavias and needs a different ECU map?

 

[Team-Joker]

Hi Muttley

The engine 110 bhp engine had the same code (AHF, I think). The gearbox has similar ratios (perhaps a little lower geared) the curves were found from the rolling road at Superchips, Buckingham, the actuator was checked and the turbo was checked and is working fine. There is no smoke and economy is unchanged. there is and no untoward mechanical noises. the timings are perfectly OK (the belt was replaced). The EGR valve is working fine.

I do not want to replace the turbo unless I am certain that changing it will do the trick. The car responds through the whole length of the accelerator travel but drives rather like a petrol car.

The torque curve has a similar shape to the Superchips curve except it does not climb so steeply (about 40% less) and max torque is delivered at slightly higher revs. Maximum power is only about 20% down. Sorry that I cannot display the curve.

Does anyone know if the accelerator potentiometer has a different value in the Octavia?

Cheers

 

[Muttley]

Did the engine come complete with turbo? I don't know if the turbo is different on the Octavia, if that is where it came from.

In your first post you said you got max torque at 4000 rpm. This is a long way from normal, max torque should be delivered at 1900 rpm. That's why I think your turbo is misbehaving, a lack of low end boost would explain the lack of power low down.

You've kept your old ECU, so the issue isn't with the accelerator sensor, it's with the engine sensors. Have they all been connected back in successfully?

Has Superchips taken boost readings, preferably using a separate boost gauge? It may be that the MAP sensor is not properly connected or has begun to fail, although you'd hope that would be picked up by the diagnostic computer - assuming that Superchips has one. If not, get it on VAG-com as soon as you can, and find out if the low end boost is what it should be.

 

[Robb1990]

Sounds like a turbo fault as said, id be checking all your VAC pipes for a start if they havnt been already. Has it been on a vag-com or even just a hand held code reader?

 

[sssstew]

yeah agreed, lets see a graph from vag com of its boost, requested vs actual.

 

[Team-Joker]

Hi

There must be some boost or engine would not give 110bhp. The complete engine plus ancillaries were installed. The original ecu is fitted so I was wondering if the ecu had been updated in the intervening period since the original Leon was introduced. I understand that the usual checks had been carried out including the boost. I had two expert teams working on this problem. Is there anyone out there from Seat who could throw some light on the problem?

Cheers

 

[Muttley]

The VNT turbo will always deliver some boost, but if the control hose is disconnected it defaults to the minimum boost setting, the one that works for maximum gas flow, that is, high revs. So you would see little boost at low revs, gradually increasing as the revs rise.

The VNT system works by restricting the turbine inlet at low revs, so that the smaller volume of exhaust gas is forced to move faster. This gets the turbine up to speed from low revs (1600 or so) rising to max boost at around 2000 rpm. As revs rise further the vanes open up to keep the boost at the max. The vane opening is set so that the widest opening is sufficient for the gas flow at maximum revs, doing away with the need for a wastegate.

This is why I think there is something wrong in the turbo control system: stuck vanes, actuator stuck, failed or not connected, N75 valve blocked, stuck or not connected and etc. The turbo was part of the replacement engine, so I'd look at that first.

To go any further with this based on your vague descriptions is likely to be unrewarding. You need to get up to 15 posts and then post the torque, HP and boost graphs, otherwise we're in the dark and can only make guesses. Or mail them to a mod, or even to me, and get them posted that way.

You have a remapped car, so I doubt if anyone from Seat, if they do look at these forums, could be of any help - you've taken it outside their specification.

 

[Team-Joker]

Thank you Muttley

I have pasted your reply and printed it out for the installers of the engine to read. (They know the car well now) I will post their thoughts on this thread when I have their response.

Cheers.