Martin’s PRV bone yard…

Well been up to loads, starting to get things finished, my pile of PRV junk went to the bone yard, and I'll soon be making another one... but as soon as I'm through these projects it will be time for a real major clear out...

P4 replica engine got a top end rebuild for various reasons. Gave it a birthday with new exhaust valves, multi-angle seats, and a quick tidy on the inlet seats… not much meat left from the factory machining (SFX engine code). The owner is getting on well with the build, so hopefully it will be kicking into life soon.





It's nearly all dressed up now, interesting the R30 UN1 gearbox input shaft has a different number of splines...

What else..

Oh… our now ageing 2.5ltr turbo engines, yes they are showing the ravages of time… One nice area of looming failure for those giving their engines more than the occasional blast – valve spring top retainers.. I hinted at this in the other thread, but I have found at least 90% probably more are suffering fatigue (cyclic loading issues with underside stress raisers). I took one to failure out of interest, and the fatigue crack was half way through the retainer cross section… now that’s food for thought…

I don’t use these retainers on my builds, but the designers obviously knew there was an issue, as they changed the design in the later 3ltr engines as you can see below. Unfortunately you can’t make the change, as they are also designed for the smaller diameter valve springs used in those engines.



Later design on the left in this photo:



You can see where and how the additional material was added in the later design to increase the core strength around the spring platform 90 deg machining feature.



As to a few other things to watch out for… cracked OE turbo headers, see a few of those now.. messes up your fuel mixture, performance etc.. not good really. Watch out for those second-hand parts, as most I’ve looked at or purchased have been u/s for this reason. It’s not really surprising, again it’s right on the cold form stress raisers… just looking for trouble with such a tight angle form etc. So next time your headers come off or the carbon is building around your header tubes next to the head, it’s quite possibly this than the gasket…





Also worth looking for better head gaskets:



Spot the difference….

...well here you go, this is one that broke earlier





.. anyway talking of design evolution... here's 3 generations of PRV rocker tubes.. which one do you have? Spot the difference, be interesting to get some feedback on anyone who has used the plain shaft in terms of wear rate, those that have will know where it comes from..



One of these days I would like to develop a billet camshaft for roller rockers, but that is going to have to wait for a good excuse for the spend!

Here is a photo of the OE 2.5ltr Renault head seat insert, as you will see it is a full radius, and the reason for the good low lift flow figures at the top of this thread. However, this also provides the reason for hitting a flow wall at higher lift, there is alwas a compromise, and clearly the designers knew this, as the seat insert would have been a more expensive item than a standard parallel insert, but cheaper than producing a more developed port form in series production - sound engineering decision... gives room for the rest of us

Sometimes when Martin talks I really do feel a bit like Joey. I recognise the words but don't quite get it

http://www.youtube.com/watch?v=DqwzvtjeYBQ

thought you were talking about the Ramones for a minute there...
or it could be Thus Spake Zarathustra

Well it's pretty simple really - tuning is the application of basic physical laws:

Make it breathe
Make it efficient
Make it reliable...

Not a lot more too it

I had used the spreadsheet off this website long time back, but handy reference for those not seen it, list of all the PRV engine types and basic details:

http://www.vectorbd.com/peugeot/v6.html

Some good and bad this weekend, below the before and after refurb and upgrade of the 3ltr engine for the Ferrari P4 replica, looking nice, and now in the back of the car. Really can’t wait to hear it crack into life properly. I had some fun with the chain adjusters and big lobe cams, but more on that later.











I had some problems with blown rockers and cams, now sorted, worth watching out for, and also good reason to make sure frequent oil changes to prevent sludge.



Some feedback from Tommy in Belgium, thanks – he kindly confirmed that the Bi Saf and A610 engine indeed share the same cam spec. and part number on the one bank. The other is different, and believe this is the balancer mass that ties in nicely with the picture Andrea in Italy kindly sent, his thread below:

http://www.renaultalpineownersclub.com/ ... 4849cc5d9a

Some other feedback was that this is all old info, so if it’s not useful or giving any insights let me know and I’ll retune, but it’s up to you to say what would be helpful ok.

As to the bad.. I had some issues with distorted 2.5ltr turbo heads, so watch out for these when buying second-hand… they will be out there, caught me out… I should have checked by offering up a cam and making sure it turned freely in the cam bores.. I didn't and then spent ages completely reworking the heads only to discover the issue when I came to do a dry build on Friday night, I wasn’t a happy bunny.. felt like this:



I had to recover them by line hone… expensive and unnecessary if you diligently do the check. Just a word to the wise..







Now assembled to the block…



Sun is out now, so off to do something useful!

Plenty of twisted heads around for sure. Sometimes twist when removed from a running engine??!!

I think they maybe have had a good roasting in the past.......?

Yes usually, and on this set more than likely as they are from an ex-Berex development engine; so probably rather punished... just I should have checked, and didn't as they were supplied torque up the middle bolts and they span nice and free... Interestingly though, I have had to skim front and back to eliminate twist in the past, but the cam bores were fine, no issue... Banana castings . They are a bit of an open internal casting, and have seen distortion in the chamber as well, so guess prone to it...

Well this is a bit of old material, on the theme of development of the components and a general look over some parts of our beloved PRV power unit, especially as they changed over time, and some odd tweaks 

Water circuit, the old arrangement:



This tends to bias the flow to one bank than the other, and this was subsequently changed in the later 3ltr engines to the arrangement seen in the pictures above for the P4 replica build, worth comparing. The story of the PRV development is there in front of us to look at and respect, as the development effort that went into these changes must have come quite slowly where production cost was key clearly.

There were also significant developments on the water pump as well, from a simple paddle design that is very in efficient and prone to cavitation (and the reason for the pitted corrosion seen here) especially at higher rpm – worth noting the pulley speeds were also changed, which gives a clue.



Compare the later design 3ltr pump with the much revised and improved efficiency, pump on the right at the top of the picture. Full of gunk from being left that way, but then point is the pump and housing design improvements.



You can also see the revised water steam and transfer holes in the gasket. Can also compare with the other gasket photos above, so more subtle changes… another point is the obvious bias to over cooling of the rear cylinders.



Here’s an odd one and still needs some consideration:



If you look at the main and big end oil drillings, you will see they have been timed completely differently from the 2.5ltr turbo crank to the later 3ltr crank. Indeed, the 3ltr cranks have variation as well, note the higher power versions and 24V not pictured here.

Here’s a tweak you can do if you are prepared to do the work, removing the flow restriction in the exhaust header branches – from this:





To this:







However it is a lot of work, and I don’t do this anymore as separate headers really are the way to go.

Whilst on the exhaust system, losses and back pressure post turbine in the turbo are quite important, and easily addressed as below (OE on the right):







Here’s a slight mod in the oil pump housing:

Some other good links on here, and else where worth a browse:

Bi-turbo build and Youtube links:
http://forums.turbobricks.com/showthread.php?t=190684

Some of my previous turbo head mod results and info:
http://www.renaultalpineownersclub.com/ ... 2&start=15

Turbo discussions, the good old days:
http://www.renaultalpineownersclub.com/ ... c&start=30

Past rolling road discussions and results:
http://www.renaultalpineownersclub.com/ ... c&start=15

Turbo match, just for a bit of fun read:
http://www.renaultalpineownersclub.com/ ... c&start=30

http://www.renaultalpineownersclub.com/ ... &start=180

And of course a real blast from the past, the 3ltr thread:
http://www.renaultalpineownersclub.com/ ... 5&start=90

Excellent link this well done Andrea.., good photos on the various engine standards and the cars, definitely worth looking at even if you are not particularly into engines per se:
http://www.delorean.fr/forum/viewtopic.php?p=72627

good works Martin
...and my link is old and has some incorrect details ^^ i learnt a lot more since then..

BTW, Martin, while we talk ^^ ...
I'm still working on mapping good my turbo prv with the megasquirt, and waiting some new wideband sensor.

regardind the atmo PRV i am building, the one with cams etc, here the last arrived items

280deg cams. In the end like you know I went with the germans, and i regrinded the original cams of the ZN3J engine, because they are little different on an end, for connecting the balancing mechanism so i can retain it if want.


91mm Forged pistons, evenfiring version, Italian made 10,8:1 cr . I sent them an original piston, an head casting . Very satisfied by the results, price and time to wait anyone need them ?







Now i'm finally read to start assembly, i have everthing and the car is ready to receive it...

Martin,
Where did you find...on which model... the crank pulley on the 3ltr. for the P4 & does it,s smaller diam. not effect the alternater output...especially at tickover.

Hi Andrea

Looking good, should be a nice build

Only thing I would watch is the protrusion into the combustion space, it tends to disrupt the flame from propagation and you may need to run more ignition advance. The 3ltr chamber has quite slow burn characteristic already compared to the 2.5ltr given the diameter, flame front disturbance and the larger surface area. What this chamber really needs is positive turbulence control i.e. squish, this is where the 24V chamber wins over the 12V.

I had this issue with high compression n/a Fiat engines, and the technology is now closer to reducing the protrusion into the chamber and running lower CRs. Best way of testing is the hydrocarbon content than O2 sensing.

Twin spark arrangement would help, and this may really make this engine competitive.

Here's an old discussion I had with Guy Croft some time back on the burn characteristic:

http://www.guy-croft.com/viewtopic.php?f=13&t=1628

Will you be running the standard 3ltr valve spring? I think it would be wise to check for coil bound, I would make sure you have about 60-80 thou minimum between coils. I don’t push the standard springs any further than 9mm full lift on the later 3ltrs heads for this reason.

Should be a fun engine though, keep posting

Martin,
Where did you find...on which model... the crank pulley on the 3ltr. for the P4 & does it,s smaller diam. not effect the alternater output...especially at tickover.

Hope you are well.

That's an OE 3ltr pulley with the front part of the pulley parted off on a lathe. Yes much smaller, but I also ran a smaller pulley on the alternator, but have run this arrangement on a GTA ok. Will see, but if Chris has a problem, will then reduce the size of his alternator pulley to run it faster.

Hi, Martin,
Things are ok. over here...just installing another engine in a customers Alpine...then I,ll get on with the update & developement off my 24vl. as you know from speaking with Chris I have changed from Renix to Megasquirt with wideband & the differance is unbelievable...the engine is so sensative on the TB,s that it has to run on an O2 sensor...also because they are non vaccum TB,s the engine does not produce enough vaccum & hence the brakes are s..t so I,m building twin master cyl. pedal boxes based on the std. pedal arrangement...maybe off interest to the motorsport guys...just read your post about your talk with Guy...as you know Guy & I go back a long way to when I was building BMW modified engines...was to go to Lincoln on my way back from the Scottish Highlands...last week, but with one thing & holiday trafic by the time I got to jun.40 on the M6 it was to late...you know Guy he,s not backward at coming forward...I,ll leave him to cool down & then e-mail.
Cheers Eddie.