[doc] #2727 Twin Turbo Progress

[Martin Gutkowski - DMC Ltd <martin@xxxxxxxxxxxxxx>]

Hi All

Harking back to a week prior to Eurofest, I posted some photos of my 
friend Rich's #2727 twin turbo engine that we've been building. Quick 
synopsis: 2458cc Renault 25 Turbo even fire EFI engine built into 
DeLorean block with a couple of Alpine GTA bits and an Island twin turbo 
kit. We added a pair of intercoolers and just prior to Eurofest, fell 
foul of a dead turbo (mucho smoko). The project has been on hold while 
other tasks were cleared following three shows on the trot but in the 
past week, she's had a couple of donor turbos fitted from Mazda 323's 
(still the IHI RHB52 but water cooled - chosen for the capacity of the 
donor engine (1.5 litre) and the factory boost of 9psi). No photos 
because, frankly, it looks exactly mthe same as the ones I posted back 
then...

http://www.delorean.co.uk/DSCN2233.JPG
http://www.delorean.co.uk/DSCN2234.JPG
http://www.delorean.co.uk/DSCN2235.JPG
http://www.delorean.co.uk/DSCN2236.JPG
http://www.delorean.co.uk/DSCN2237.JPG

...but it sure as hell goes better.

Currently we have the map that was created on the rolling road under 
normal aspiration, and an ignition map from some other engine set with a 
MAP limit of 2 bar (1 bar of boost). The MAP sensor Rich bought for the 
engine is from a Ford Cosworth and in calibration, we discovered it will 
actually measure nearly 20psi of boost despite being a 2 bar sensor (do 
you like the constantly flicking between bar and PSI? :-) The ecu we're 
using has an adaptive mode, and with the addition of a bosch wideband 
lambda sensor, does a remarkable job of writing its own map based purely 
on driving the thing.

We decided to take the car on a 4 mile trip to the nearest petrol 
station and Rich drove while I watched the ECU outputs like a hawk. This 
was on the hottest July day since records began..... on a turbo car 
running high boost..... yikes. (just shy of 100F). I say Yikes because I 
have a live readout of Manifold Air Temperature and as the boost 
approached 15 psi (1 bar), the ECU was telling me we had air at nearly 
80 degrees C entering the engine (176F). I think those intercoolers are 
going to be moved downwards...

After a bit of wastegate messing, we got it limiting at first 3psi, then 
8psi, then hitting the ECU's boost limit (set to 200kPa - well the 
software works in kPa - keep up!) at 5000rpm. Gutless at bottom end, and 
obviously in need of a proper tuning session, I am however happy to 
report that it shows all the signs of being a very quick car. The boost 
comes in at as low as 1200rpm, and will really benefit from an ECU 
controlled boost control valve to stop the wastegates opening at all 
till the target boost is reached - currently it's lovely and progressive 
but I'm sure we can gain some torque with more boost lower down in the 
revs.

And much as I hate the film, the fast'n'furious dump valve noises really 
put a grin on yer face in a DeLorean :-D

Martin






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