[DML] Turbos, transmissions etc
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[DML] Turbos, transmissions etc

Hi All,

Right, lots to say, lots to reply to (I think Ben had the same trouble!)

I talked at length today to a diamond bloke who we're now getting our 
stage II camshafts from. This guy has been into the PRV since the late 
70's and has built and raced several engines. He is getting more than 
270bhp from a carb'd 2.6. Work that out! (Okay it's a race engine and 
needs rebuilding after every season).

He is also the UK's foremost specialist in the UN1 gearbox. I don't 
agree with Dave T's analysis that the manual tranny can only handle 
200hp without problems, and this was confirmed for me today. The 
DeLorean has a lower ratio 5th than the Esprit (for example) and V8 
Esprit owners find that it's 5th that pings off first, followed by the 
input shaft, diff and driveshaft couplers in that order. I suspect we'll 
start snapping driveshafts before losing the diff though - Esprit ones 
are somwhat larger than DeLorean ones! The stock DeLorean transmission 
is good for up to 300hp. Clever use of progressive boost control on a 
turbo engine can keep the gearbox healthy by not hitting it with a 
sudden surge of power. Although this takes some of the fun out of a 
powerful turbo engine! "More than 350 and you will break it" were his 
exact words.

You mention input shaft by Bell Performance (it's not Inconel BTW - 
Inconel is only really special for corrosion resistance, not needed in a 
gearbox). Our guy does something similar but sticks to the original 
pattern and does entire gearsets. he was instrumental in the development 
of the Quaife LSD for the UN1. His gearset will take the 'box to over 
500hp capable for £2000 or thereabouts. He also confiemed that Lotus are 
lying through their teeth when they say the esprit box has strengthened 
internals. he had Renault and Lotus box internals tested by a 
metallurgist who confirmed they're identical.

Rob Grady's also correct, 2nd synchro hubs are getting scarce from 
Renault too.

Right - on to turbos...

I've set up my friend's Island kit ( the only one in the UK as far as we 
know) but do not know if the dizzy was re-curved. At the time it was 
out, we didn't know to check, but I'll be stripping it out to do a 25 
turbo conversion using the twin turno system so will check then. I 
thought the enrichment setup with the lambda system was really 
mickey-mouse and never worked well anyway (on his car). I've got rid of 
the lambda system and use the CPR's ports to enrich under boost 
(enriches when foremost port is at a higher pressure than rearmost, 
discovered it -does- carry on into positive aspiration. Rather well in 
fact. He gets about 13mpg , but it keep s cool and goes like a scalded 
cat. Shame it's an auto! - though that's changing when we do the conversion)

Renault have specific part numbers for the head gaskets according to 
engine type, although obviously the three different bores have three 
different gaskets, there is a specific reference to the Z7U engine which 
is the 25 turbo. Interestingly, the 3 litre engines (93mm bore) are 
listed as haivng a slightly thinner gasket (by 0.24mm) than the 88 and 
91's, regardless of aspiration.

I've changed my opinion on  turboing the stock DeLorean engine based on 
what I learnt today - but it still means changing most parts of the 
engine and doing a helluva lot of work. Here goes...

The easiest way to achieve the pistons is to have a set of odd-fire 
conrods made 10mm shorter and fit 25 turbo pistons. The odd-fire crank 
is good for over 800bhp. Yes that's correct. Unbelievable but true.

Camshafts: use those from a 25 turbo and have the gear ground into the 
left hand shaft - the boss is there but the teeth aren't cut. The timing 
offset for odd-fire is nothing more than the right-hand cam sprocket 
being offset by 15 degrees, so just refit as normal into the D engine. 
This will give equal valve timing on both banks and will make the engine 
shake a little, but makes it suitable for turbos. Then worry about the 
ignition and fuelling....

As far as the figures on turboing go - I think 200 is the upper limit 
for turboing a stock D engine (Island, BAE, DMC Only). It makes sense 
that if you can tickle that with normal aspiration, which is all about 
breathing better, you should be able to achieve it with a modest level 
of positive aspiration.

Best Wishes

DeLorean Motor Cars Ltd

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