Quote:
Originally Posted by Adrian D
Hold on, it runs 14-15 PSI bone stock, at least 3 different cars have shown that. Mudmonster also had a report on the stock boost.
|
My boost gauge shows about 10psig at 110km/hr. If I put my foot down (WOT) it goes to over 25psig. IIRC as much as 28- 30psig before it reduces by way of ECU control.
I believe the waste gate is set at what it runs up to. Try disconnecting the waste gate & see what under load it goes to.
I have been told mine is one of the very last VM 2.5td's that went in XJ's. The only non stock thing about mine is the EGR is disconnected.
I have an EGT gauge (pre turbo ~ post turbo temps are useless for monitoring for engine protection) that I watch when fully loaded on hill climbs etc.
You only use max boost under full load so what it "runs at" under light loads is not relevant & has no positive benefit to increase it.
If you were to use a larger turbo all you are likely to do is increase turbo lag. A cheaper way to do this would be to change the trim of the fans in the turbo.
The later engines I have been told have their ECU tweaked a bit & are supposed to have a little more torque, this is not claimed by jeep though. This occured with the later ECU's. ~ there are 3 different ECU's fitted to the VM 2.5td. Also the sensor was moved from pre turbo to post turbo with one of the updates.
I have asked several times on here about the different ECU's but cant find any one on AJOR who knows the details of what changed with each ECU change.
Do you have any info about this Adrian? By having that information I may be able to use a tuning chip I have.
Unless you can modify the ECU ~ chip or re-flash (?) or some how modify the MAP/inlet temp sensor signal, the ECU will not let the extra fuel in to match what would be needed with higher inlet flows/pressures.
MM tried larger pipes to & from the inter-cooler. Reading his posts, it appears that the most significant effect was to increase the turbo lag. This is to be expected by increasing the inlet flow path volume.
I have been recently trying to see if with a little electronics, the sensor signal can be modified to allow extra fuel at high boosts to continue & so stop the pressure drop back that I see after a short bit of WOT. Unless you do that there is little benefit to be gained from a manifold &/or turbo change. The biggest problem is that you may just end up causing a lot of black smoke when you first accelerate & little improvement when you need it.
Your comments about Peugeot diesel engines are like comparing apples with oranges. IIRC they have a different injection set up & different control. There is a version of the VM 2.5tdi that has a belt drive OHC. Dont think any of them came to Australia in other cars though. Dont know if the head off them can go on ours.
The ECU is designed to prevent the sort of changes that the OP is asking about from providing much benefit.
You dont get any significant benefit unless you can get more fuel in.
To quote Optical from the link Murray has given;
"then theres things like boost, but you have to mess with fueling and i wouldnt wanna mess too much with the VM"
I think Optical had at least 10 years experience tinkering with engines when he posted that.
My comments are based on about 30 years of tinkering with diesel engines, mainly earth moving equipment. I have put turbo's on N/A diesel engines & tweaked other ones. They are a lot different to petrol engines.
Unfortunately too many think that bigger is better & dont consider the complexities of electronic control.
