Re: [doc] Re: A few questions

[Nick Tomlinson <nickandkathryntomlinson@xxxx>]

Hi Martin, I wasn't going into details as such just glorified highlights without going into a major thread although I do like to chat about these things.

The degree variation on the 'V'. The crank itself is rotationally balanced due to the counterweights so that the rotaional balance is smooth (not accounting for crank-flex at natural frequency harmonic rpm and no. of bearings etc.) I meant balance as in equal firing hence the da-dum da-dum da-dum sound more noticeable when the engine is at curb idle. To explain about the 'V' is hard without a diagram. 

A great basic article on engine design is in Practical Classics June edition I think. I still have my copy. I'll scan it in and e-mail it to you. It mentions the PRV about having the wrong 'V' angle. (I know others have narrow angle 'V's such as VW VR6 and Lancias V4 but the solutions here tend to ave balance shafts to equalise the vibrations.

Other things would also have been applied such as lowered compression ratio, uprated oil cooling (oil cooler and/ or spray jets to spray oil underneath pistons), dump valves, amal valves etc would be applied..

The intercoolers are ideally mounted on the front of the car to maximise ram-air through the heat exchanger (intercooler) but unfortunately with long pipes this will enhance the turbo-lag associated. This is why pipe runs should be kept as short as possible with nice curves instead of sharp 90 degree bends. The air-flow through the intercoolers on the 'd' would be a bit naff and I would have put 2 air scoops underneath the car to direct air through them.....who knows what improvements would have been made?

I've seen the K-Star system used before. It would be a challnge to write the software for a new ecu to overcome these 'bodges'.

8psi is approx 0.55 bar. 

I'll dig out the article and e-mail it to you.

Regards,

Nick.


Martin Gutkowski <webmaster@xxxx> wrote:


Nick Tomlinson wrote:

>Hi, of course the turbo on this type of engine is a bodge as it was an afterthought to try and increase the engine power prior to the release of the Twin-Turbo. 
>
The Island kit is actually based on the Legend twin prototype.

>The engine is a V6 where the V is space 90 degrees apart. The V should really be 60 degrees for the pistons to be equally spaced apart. 
>
How do you work that out? 90, 60, or even 0 degrees (inline), makes no 
difference AFAIK - edumacate me?

>(Originally the engine was designed to be a V8 but the oil crisis made them chop 2 cylinders off!) The top of the distributor looks wierd as the HT points are not equally spaced apart. This is because the firing stroke is not even. The engine will run but the result is an unequal balanced engine with not the best gas-flow in the world. 
>
Actuallty the odd-fire PRV is perfectly balanced thanks to 
counterweights on the crankshaft

>The Renault turbo and delorean turbo would have to have its innards (crank) re-designed to give equal firing to make the gas flow a lot more even to satisfy the turbo design. 
>
Correct, the Renault 25 turbo has an even firing crank. But it goes a 
lot further than that.

>Oh I sound boring now....bla bla bla....Another thing about the turbo's is that there is no air-air intercooling. If we consider Boyles Law (ideal gas) Pv=nrt if the air pressure is
> increased for a set volume then there will be an increase in gas (simplification here I know as the volume in a cylinder changes due to the stroke of the piston) and this can lead to high temperature detonation sproblems. If you have a look on the true delorean there are intercoolers between the turbos and the inlet manifold. 
>
This was actually somethig that enver worked properly for Legend. If you 
look att the Alpines, the intercooler is moutned along the rear of the 
engine compartment and relies on air drawn up through the engine bay. I 
prefer the Lotus Chargecoolers, but that's just "mr complicated" 
here.... Intercoolers have advantages and disadcantages - the advantage 
is increasing the density of the air by cooling it after the turbo. The 
disadvantage is that the turbo has to pressurise a much bigger volume, 
which increases turbo lag. The 90bhp Citroen/Peugeot HDi engine does not 
have an intercooler for ths reason. The 110hp version which I have in my 
Xantia has an intercooler, is more powerful, cleaner, more economical 
and IMO nicer to drive, so I'm not disagreeing with you that 
intercoolers are a must :-)

>This also assumes that the air-fuel ratio at high revs with boost does not go lean. Some bodges are to re-enable the cold-start valve when full throttle is enabled (on vw engines with k-jetronic for example). 
>
The Island kit uses hobbs switches to disconnect the lambda sensor 
sending the lambda computer into "limp" (ir slightly rich) mode.The best 
solution long-term is to use the K-Star system from Milford together 
with a J&S Spark controller and knock sensor.

>In my opinion (and its an opinion) the boost pressure should not be more then 0.6-0.8Bar 
>
DeLorean engine should go no higher than 8psi boost. (14.7psi = 1 bar IIRC)

Martin

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