tuned derv ZS update

[Jay-ZS+]

Originally Posted by p_b82

I am making a guess here Jay, but i think that the rebuild with all the new bits and gubbins will prob have been more than your new engine was

Bloody hell good job your not a student too!
Reckon you could top this list pretty easy!! http://www.themgzs.co.uk/vb/showthread.php?t=13093

[p_b82]

hehe yes i think that you are right there..... i have avoided doing all the sums for a while, it scared me last time i did it about 2 years ago lol (that was before the 1st HGF )

suppose it is one advantage of only payring rent atm, and having a job where i am sent lots of places so i have very little living expenses.... tho the home front is about to change soon...

[p_b82]

Initial testing suggests that we do have high exhuast manifold pressure, but the gauge/reader needs a minor tweak as we need more cooling pipework before the switch to plastic for the boost gauge.

so looks like a method to bleed off some pressure is the way to go.... hopefully more info/results next week.

[peterzs]

How did the Seat Derv's in the BTCC get over EMP, they used to go like stink and they are one of the reasons I got my derv.

Must admit I thought it was the BMW derv engine not the L series ( just shows how much I knew) Saying that I'm pleased with the way it goes.

Look forward to the next lot of results, hope its not too costly this time.

[p_b82]

probably by running a turbo with VNT.

it is basically a huge turbo (as denoted by the GT20 or GT22 starting numbers), but by changing the vane angle you get it to behave like a small one. so you get high resistance at low rpm with the vanes closed, and low restance at high rpm with the vanes open.

That means it spools as fast as our little GT 15 family units, but are big enough to flow enough exhaust gas and drive the compressor like a fixed vane GT 22 unit. it results in the ability for well over 200bhp - assuming that the fuel is there.

All modern diesel engines now use VNT units, they are the way forward, but they are more fragile than 'old style' fixed ones. which means this like fuelling and boost is much more important to get right early etc.

Controlling it on the L-series is not easy however, but there are a few people trying to do it as we speak. either has to be done via a seperate control module, or tie it into the EGR vavle controller - but for that you have to remove the EGR, so that would fail MOT on a Mk2 as that can't be disabled yet

We are getting there, and this last little bit will be cheaper than the rebuild was for sure

[p_b82]

been a few days so figured i would pop an update up...

the pressure reading system is proving to be a bit of a PITA to fabricate, as it keeps melting the oil feed pipe Matt is using to connect the brake line he has attached to a plate in the exhaust manifold.

so even tho there is no gas movement as it is sealed it is still transfering a hell of a lot of heat along it.

I had hoped to pick the car up this week, but my schedule will not allow this now, so prob will be next week sometime (on my way back down from hull most probably)....

will probably now also just use a ball and spring based boost controller to dump any excess pressure rather than worry too much about external wastegates, as it looks like heat is going to be too much of a factor, and i am still concerned about dumping too much gas with summit like an external wastegate...

[peterzs]

Cant you just turn the boost down, ( I dont know anything about boost etc, only that our whiz kid fitter, who used to have a big American muscle car and took it to Santa Pod, boosted mine up a bit)

If your turbo is pushing out 25 psi is it possible to cut it back a bit. Cant remember what he pushed mine up to, think it was 2 psi above whatever. Anymore and he said it caused the engine to knock.

Best of luck and hope its sorted.

[p_b82]

Theoretically i could turn the boost down, but that defeats the object of having the hybrid turbo - that has been designed to cope with 28PSI on the intake side of things. (I am running it at around 25/26 PSI atm

the problem is that the internal wastegate is too small to bypass enough of the gas from the hot side, but controlling EMP via boost pressure (intake) is not actually a sensible way to sort the problem - it works by reducing the effective combustion of the fuel by removing air, but this method theoretically would be more effective, as it is dumping the excess pressure post combustion.

Eg if i reduce boost i have to reduce fueling as otherwise the fuel wont be fully combusted, i will get higher smoke, and see the EGT's rise again. At the moment they are nice 'low' 750C while under sustained full throttle - well within turbo temp tollerances and the manifold itself. (i had seem 850 with it still climbing before i backed off the throttle in the past - and that is way too hot!)

I am still quite surprised by the knock comment - diesels dont knock usually as there is no way for the fuel to ignite before the compression is at the max - and an excess of air just results in more complete combustion with a diesel. (out the factory they all run lean as it is hence no smoke and better emissons)

There is no point turning your turbo above 19PSI as the turbo itself becomes inefficient and can't take the strain of the 150K+ rpms that that sort of boost is asking of it. Seen a few pics on .org where the housing starts to crack after a while, and the bearing give up the ghost as they are too hot and dont have enough lubrication...

Car is 99% there now, just this last little niggle.....

[peterzs]

Suspect he was just keeping it safe.

Glad your almost there with your one.

Santa Pod next??????

[p_b82]

Right I have picked the car up and done a 100 miles in it to get me back home and get some readings for the EMP...

the news is both good and bad:
the bad news is that we have got high EMP, on full throttle in 3/4/5th it is above 2.5 bar - i guess 2.75 to 3.0 as it went off the end of the guage.

the Good news is that now we know this we are able to work out a solution, and if you dont use full throttle and gradually build the boost by rolling the accelerator the EMP keeps lower (but still higher than it should be)

so while we\I do some research and bandy some thoughts around on how to correct it, i wont be thrashing the car - so no Pod just yet Peter

Maybe this needs a seperate thread, but any EMP possible solutions please send me a postcard with the thoughts and method to solve it.

Ideally we want something like an idle control vavle that opens up gradually as the pressure against it increases but closes off nice and slowly as pressure drops.

Other requirements
It has to cope with exhaust temps of around 800C
It has to cope with sooty exhaust gases
It can't dump too much gas from bypassing the turbo and stalling it

Ay thoughts let me know... i am a bit stumped, i have a few ideas but nothing that in my mind will be easy to implement without a large amount of time\effort\experimentation