[DML] Re: PRV Performance - Set me straight please

["content22207" <brobertson@xxxxxxxxxxxx>]

I am of the opinion that domestic F series is a counterproductive and
even harmful application of the Douvrin design. How else to explain
generally unhappy North American experience while Europeans seem to
love the engine. The PRV over here has a negative reputation totally
disproportionate to the small number actually imported.

Biggest flaw I see in the North American version is heat. Irrespective
of any other advantages or disadvantages, a richer fuel mixture simply
burns cooler. Domestic PRV's are hot as a firecracker. I once got 2nd
degree burns on my fingertips touching a stock DeLorean engine! My
Renault block (Z7, European spec) never ran as hot as a B28F, and my
current carbureted Peugeot version was running so cool this winter
that I bumped the thermostat up to 195 degrees (versus 188 degrees F
spec). 

All that heat can't be healthy for gaskets and seals, or even the
aluminum itself. Don't forget that PRV's, especially in K Jetronic
trim, are very dependent on tight gasketing. I also wonder if imfamous
PRV "oil problems" are exacerbated by barbequing the stuff.  
Americans seem to be the only people complaining.

Heat is also Enemy #1 for alternators (what's the single most common
engine accessory failure experienced by DeLorean owners...). 

Europeans did several things on their PRV's much better than US
regulations allowed:
- Kept compression high. Gives you the same benefits of forced
induction without any of the complications. Does require a richer
mixture, though.
- Used higher lift cams. Allows more mixture into the cylinders.
- Didn't monkey with fuel/air ratios (engine warmed up -- key word
"warm", not "hot").
- Didn't force the engine to breathe its own exhaust (EGR). Didn't try
to burn anything where nothing was never intended to burn (exhaust
system via catalytic converter and smog pump).
Simple things that add up to 145-150 HP. B280 redesign bumped
compression all the way to 10:1, increasing HP to 170 (in conjunction
with different crank/bearings, valve train, and yes -- EFI).

One last thought: engineering that seems terminally wierd on a K
Jetronic equipped PRV (Valley of Death, inaccessible ignition
distributor, etc) makes perfect sense when you deal with the same
components on a non-K Jetronic application. Douvrin did not design the
engine for the fuel injection it later inherited. Volvo corrected much
of that in the B280 redesign.

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "Rick" <rdevaux@xxxx> wrote:
> 
> 
> Gary, The mods I'm going to do are changing my CPR to one that has 
> vacuum enrichment, replace my ign distributor with a B28E distributor 
> which eliminates the delay solenoid set up, higher compression 
> pistons, head porting, B28E cams and headers with a 2.5 inch hi-flo 
> exhaust without a cat.  I just want to take what the basic B28 could 
> be without going "exotic".  No turbo, no Megasquirt, I want to keep 
> it as basic as possible.  I thought the B28E cams and pistons would 
> be a good start, keeping the engine stock and dependable.  I also 
> want to keep the K-Jet so that when problems with the fuel system do 
> develop, they'll be reasonable to deal with.  My engine is rated the 
> same as the Delorean, 130 hp.  How are folks, DMUK and DMCH, getting 
> their hp boosts from 130 to 150-190?  Are there rising-rate pressure 
> regulators available that could be considered?  Thanks very much, Rick
> 









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