Low top speed (2.5 DSE)

[mcapinha]

Last weekend I was finally able to find the diesel leak on my DSE that was caused by an improperly tightened injector nut. Also gave some attention to the intercooler pipes that were wet with oil (and if there's oil coming out, they were certainly loosing pressure too) and now the DSE runs very well, with lots of power (I have a PSI box).
Took it for a run today and I couldn't get it past 92mph (150km/h). Since it feels like every one of the 160 horseys are there, any thoughts on what could be causing a low top speed?
The DSE is a manual, running on 16'' GG AT2s.

 

[Teamemmenracing]

92 mph ........ thats about all my 2.5 DSE manages as well

 

[Datatek]

What revs was it showing at 92mph?

 

[dogsbody]

There are three main reasons for the low top speed;
weight
shape
engine

 

[Canyon]

92mph? You were on a track of course, you forgot to mention!

 

[mcapinha]

Data,
I'll try to let you know tomorrow, if I happen to take it out for another spin (on the private track, off course).

 

[Mike v.t.s]

There are three main reasons for the low top speed;
weight
shape
engine

I dont agree, mine is a DSE on 18's with general grabbers at2's and a PSI box and it will do 100mph without torque converter lock, i no coz i put foot down last night on the M55 on the way to blackpool to try and make it go into lock mode, from memory it was reving at around 3.800 but i might be wrong might of been slightly higher or lower.,

 

[arron beast unleashed]

my old manual dse (granted with a few mods) would do 125mph gps reading on the governor topped out.

 

[wammers]

The theoretical top speed of a DSE automatic is around 110 mph. Manual slightly less. If i am reading the gear ratios correctly. Anything above that has a tuned speedo or the wrong size wheels. Max engine RPM is 4950 (light load) fuel cut off begins at 4400 RPM under load.

 

[Datatek]

I dont agree, mine is a DSE on 18's with general grabbers at2's and a PSI box and it will do 100mph without torque converter lock, i no coz i put foot down last night on the M55 on the way to blackpool to try and make it go into lock mode, from memory it was reving at around 3.800 but i might be wrong might of been slightly higher or lower.,

If your torque convertor was not locked at 100mph you need to get the problem sorted A.S.A.P.

 

[mcapinha]

I think I've finally found out the cause of my low top speed. I installed a pressure gauge on the MAP pipe and it's reading 0.9bar under load. From what I've gathered around the interwebs, this turbo should be putting 1.2bar, so that's 25% less

I'm going to check the air filter and intercooler pipes, although I've heard that these could look OK but still have internal lamination? Is there any way to be 100% sure that the pipes are OK? I seem to remember that if I push the pipe that goes from IC to intake manifold it will collapse and choke the engine..

 

[arron beast unleashed]

boost is supposed to be checked on a annual service although never gets done, your actuator has probably gone a bit week and needs adjusting. pretty fiddly on the p38 as you need to go under it and work up through the mount, can be done with patience though. crack on.

 

[mcapinha]

That's exactly what I'm going for, after checking that everything else (pipes/filter) is OK.
From what I understand the wastegate is held by a spring. Changing the length of this spring (by tightening the nut) will force the gate to open at a higher pressure, thus increasing the boost output.
From the top of my head I think the access is OK, just by lying under the Rangie?

 

[wammers]

That's exactly what I'm going for, after checking that everything else (pipes/filter) is OK.
From what I understand the wastegate is held by a spring. Changing the length of this spring (by tightening the nut) will force the gate to open at a higher pressure, thus increasing the boost output.
From the top of my head I think the access is OK, just by lying under the Rangie?

And playing with that without setting it properly, is a REALLY good way of screwing your engine up.

 

[mcapinha]

Hmm.. I know that the pressure is off by a good margin. My idea is to slowly turn it up until it reaches 1.2 bar and I have no intention of going over that value.
Wammers, maybe I'm not looking at this correctly? I'm under the impression that as long as I keep it down to the specified boost I won't risk damaging the engine, right ?

 

[wammers]

Hmm.. I know that the pressure is off by a good margin. My idea is to slowly turn it up until it reaches 1.2 bar and I have no intention of going over that value.
Wammers, maybe I'm not looking at this correctly? I'm under the impression that as long as I keep it down to the specified boost I won't risk damaging the engine, right ?

The only way to set it properly is to load it with a known pressure, in this case 1.2 bar or 17.64 psi, 18 should do. Then adjust until flap valve is just still shut. So anything more than that unloads turbo. I have an adjustable rig for doing this. Just keeping adjusting until you think it's right is not a very good idea.

 

[arron beast unleashed]

rather than keep messing about in a tight space just buy a manual ball and spring boost controller, that way you will have full control, easy adjustment and it will get rid of waste gate creep aswel.

 

[juiceyv8]

rather than keep messing about in a tight space just buy a manual ball and spring boost controller, that way you will have full control, easy adjustment and it will get rid of waste gate creep aswel.

Then if you get a boost leak the ECU cant go into limp mode to save your wallet.....

 

[arron beast unleashed]

Then if you get a boost leak the ECU cant go into limp mode to save your wallet.....

nay, it wont effect the control by the ecu if there was a boost leak. the contoller only goes inbetween the actuator and the the boost source, it still has its map sensor where it should be and doesnt effect its operation.