PRV engine: what breaks at what speed question

[dmc6960]

In the "Ask Steve and Farrar about Carbs" thread (http://dmctalk.org/showthread.php?3084), after being asked if be bought that car, he writes...

No, I did not happen to buy "a 6K DMC with blue bumpers".
However, I have that same lower runners and it has 48mm throttle butterflies. The runners do indeed accept CIS injectors. I'm not aware of any electric injectors small enough to go into the bores provided.
I also have the air plate and fuel distributor assembly along with the injectors. I've yet to check their numbers to see if they are DMC.
Do you know what that manifold is? What size throttle butterflies does the stock DMC CIS have?
I'm certain it is CIS and not L-Jet or later.
Oh, what do you know to be the HP and torque limits of the automatic and what fails first? Second if that's addressed and at what numbers then?

And then...

It is lower runners as shown on the blue bumper although it is CIS and not EFI.
BTW... I've asked some direct and should be reasonably easy questions, do you guys like to not share knowledge or is it my breath? ;-)

And here is the engine picture from that car for reference...
5G45Kf5W13M53J83N9c4tfc9e2ba3fa5a1008.jpg

The way he describes it it sure sounds like the car in question. I wouldn't blame him for flat out denying it though!

Another relavent quote which REALLY sounds like that car...

Mine has the upper rectangular vessels, a type of molded plastic, on each side, remove-able and the lower runners "spigot'd" so that they are coupled to the upper non-metal boxes via rubber hoses clamped onto the three spigots at the bottom of the boxes. Maybe my manifold is from something else. Heck, maybe the engine is as well. I suppose I should find out if this engine is a factory PRV for the DMC.
Other than this deviation and the carb in place of all the CIS stuff, it appears to be a stock DMC engine.
I like it better than the ebay stock piece as it leaves me the option of connecting carbs on their ~ 4.5" centers, or removing the "lower manifold/runners" and screwing them directly to the heads.
I'll take it completely apart once I start fabbing up my carb setup and snap some pix.
Does a engine chart exist for the purpose of identifying these engines via their casting and/or stamped numbers and where are they located?

Then he goes on and on about not getting the information he's asking, despite everyone in the thread pretty much flat out saying they have no idea what he's asking for. Andy directly asks for pictures twice and is ignored, followed by posts saying how nobody is telling him what he wants.

Another interesting note, he is very interested in the automatic transmission filter. Does anyone remember if that blue bumper car was auto or manual?

[82DMC12]

Another interesting note, he is very interested in the automatic transmission filter. Does anyone remember if that blue bumper car was auto or manual?

Interesting that someone so flat-out concerned with every last tenth of horsepower available would get an AT. But I think you are right, it's blue bumper.

Not to say that's a bad thing. Sure looks interesting and I wonder if it even runs well. I'd like to see more pics of it and find out what else has been Joey Gowdy'd on that thing. Someone needs to tear that car down and do it right. If "Earl" can do it, then great.

Andy

[LEVY]

I wouldn't blame him either!

In the "Ask Steve and Farrar about Carbs" thread (http://dmctalk.org/showthread.php?3084), after being asked if be bought that car, he writes...



And then...



And here is the engine picture from that car for reference...
5G45Kf5W13M53J83N9c4tfc9e2ba3fa5a1008.jpg

The way he describes it it sure sounds like the car in question. I wouldn't blame him for flat out denying it though!
Another relavent quote which REALLY sounds like that car...



Then he goes on and on about not getting the information he's asking, despite everyone in the thread pretty much flat out saying they have no idea what he's asking for. Andy directly asks for pictures twice and is ignored, followed by posts saying how nobody is telling him what he wants.

Another interesting note, he is very interested in the automatic transmission filter. Does anyone remember if that blue bumper car was auto or manual?

[MFaulks]

I stumbled across Guy Croft's forum and was reading the PRV thread there just a few minutes ago. I'm a bit confused as to the stock piston and what appears to be non-existent squish. Does the stock piston actually positive or zero deck or is it what I think it is, a reverse dished piston with actual negative deck? You may be interested in reviewing that thread as the carbon formation and other various chamber patterns are quite peculiar.

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

I think I'll sign up and chime in on this thread. I think the chambers and crowns should be dead smooth with that inexplicable half moon gouge filled in. It also appears to need flattops so as to have at least some squish. I do think the injector is indeed too close to the valve head although GC doesn't seem to think so. Maybe if the intake seat was 45 degrees the affect wouldn't be so pronounced. I don't know the valve material, but, probably not too much of a concern on that turbo engine if using Nimonic 80A.

How much larger is the stock piston bore than the diameter of the chamber or are they the same size with respect to the cylinder wall?

All I want to do with the stock engine is optimize what is there first without turning a bolt or nut to access the engine's internals. I'm gathering pieces to do headers with skinny long primaries and already have some nice tight collectors. My CIS is FUBAR at this point so I'm going to use 2 racks of 3's and see how cold the pulse tuned runners will get.

If that goes well, maybe slip in some flattops, port the heads and detail the chambers while the heads are off.

BTW... nice pistons and they look intelligent. I notice GC does not seem to polish his chambers and crowns dead smooth. I certainly do and always have since nobody has ever given me any reason to support chamber/crown roughness or sharp edges. It appears from the pix that your pistons do not have any sharp edges, which is nice as most Hi-Po pistons are merely kits as far as I'm concerned. Will you polish the crowns dead smooth?

Most of my experience is with hemi's, semi-hemi's and wedge's, although I've built many others including some very fast side valves. NA, blown and NOS. The other guy in my shop is a pent roof wizard. I do like the prv chamber and it does appear to have much promise.

Also, why does the DMC engine have different cam timing from one bank to the other? I know most of the other versions do not. Are the ports, head or intake runners, actually different from one bank to the other as has been suggested to me?

I also haven't found a spec on the rocker arm ratio's and they appear nearly 2:1 and almost with room for rollers, especially if bumping down the ratio just a tiny bit. Do you know the ratio? Rollers on both ends and a shoe box looking lobe would be teats.

Have you ever seen a header for the odd fire prv with multiple crossovers, with long skinny primaries and a tight long collector? I'd be interested in buying a set already made even if I had to cut and section them to fit the DMC. Even without crossovers or suitable collectors, it would still save me some time

Earl,

The thread you stumbled across is the one I wrote to GC's Q&As back in 2008. I'm happy to discuss the detail behind this with you directly anytime. I have done much since, and stand behind the fact the chamber really doesn't burn that well. It does have some nice flow characteristics (it's effectively a bi-hemi chamber), and I can back that up with flow numbers some I have already posted link below, and will add the 3ltr head numbers when I get the chance to write it all up. Going back to one of your other questions, this should allow you to asses your intake / runner questions. I do have the volumes, and port velocity probe data taken at 10" depression. DCUK Martin kindly pointed me to some of the threads here; I don't tend to switch about too many forums as my time is some what challenged.

http://www.renaultalpineownersclub.c...t=5612&start=0
http://www.renaultalpineownersclub.c...pic.php?t=4899

I started the thread to share knowledge, but sadly have found it sounds a bit like me talking to myself more than anything else... pity.. Lots more I can put up there and will do in time, noting the intention hadn't been to push the parts (cams etc - cnc ground and have the files, so happy to share cam cards) I have developed for myself over the years, but to help others not go down the blind alleys I have done. The rocker ratio isn't exactly 1.5:1 as it varies as the cam sweeps the follower, and there are issues with the geometry and cam profile to get symmetrical lift profiles from 1-3 to 4-6. I want to do a roller rocker profile, as I believe this is really the way to go, but as a development cam from billet is going to be very expensive makes it prohibitive for just one set; noting you can't use a chilled cast as I do normally given the contact pressures encountered. So if this is something you wanted to get involved to reduce costs through scale, then let me know. There is a roller rocker that gives approx ratio of 1.6:1 that suits the hardware, so that makes a great start.

The ports and runner lengths are the same bank to bank on all the variants of the engine. The subtleties on the cams is the relationship of the rocker arm orientation to the cam lobe - leading and lagging effectively if you can picture my meaning. This results from the head casting actually not being handed, they share the same core casting, and just the external cast detail is handed. Hence you will see that on one side the exhaust ports face forward, and on the other bank they face to the back of the engine.... The cast cam blank and profile can be used either in an even or odd fire engine. The factory data isn't well specified for cam timing, and I have digitised most profiles, and none of the OE profiles I have tested are equal 1-3 to 4-6.

To get squish in the chamber the heads need to be welded. The piston crown comes to the top of the liner in all cases. I have skimmed the heads to the point of getting flat land area to take advantage of flat top pistons, but it takes quite a bit of material removal to do it. In the majority of my builds I'm forced induction, so not as worried about it as n/a, as I gain mixture motion in other ways. Note the ports do not induce much swirl, and fuel wetting is an issue. Correct the 45 deg seat is much better in this regard, and this is part of the advantage of the 3ltr head in standard form. I have also tried 55 deg seats with special valves, and this was for a strip motor, not ideal on the road.

I wouldn't take the OE odd fire rods to 8200rpm, they will fail certainly from experience in forced induction applications, and the odd fire crank is chocolate.. even fire is much better in this regard. Depending the cam profile, ramp rates, and closing profile the OE springs really need consideration. If you want I can post up their characteristic curves.

Regards,
Martin

[EarlHickey]

Thank you. It's always amazed me when people who don't have any answers insist on chiming in without any constructive or factual input whatsoever, and the "moderation" here allows the resulting destructive chaos to stand, repeatedly. I will be speaking to you very soon and I think you may be interested in some of my recent projects. I seriously appreciate your willingness to openly share and look forward to one day making your acquaintance.

I will indeed take you up on the offer as I would like to get some serious software on top of what appears to me to be a thoroughbred choked down by some of the worst of EPA mandated malarkey, as well as some very poor design choices.

I recently made a batch of rockers with rollers on each end, they ride on needles and plan on doing some oiling modifications. You know what else has to happen to make use of them as well. That is in the works and i suspect it may take a few stabs to fully exploit the small port long rod geometry while conserving as much energy as possible.
I'm certainly interested in the possibility of a cooperative project and I sure won't buy anything from any supplier that finds it "distasteful" to merely post performance product specs, and I mean EVER.

The dual axis poly hemi seems to completely lack ANY squish whatsoever and that is a huge, but looks correctable, flaw in my humble opinion.

Have you run this chamber with tightly squishing (20 thou or so with Silovlites) flattops? I think that will be my approach and I'm going to do a bit reshaping on the chambers to make it worthwhile. The 30 degree seats are silly and I'll dig back and review where I saw discussion on the valve head shapes, intuitively, I want a 30-32 degree tulip with modified chamber (partially tubbed) although it is very possible that 20-26 degree may end up doing the serious business.

Earl,

The thread you stumbled across is the one I wrote to GC's Q&As back in 2008. I'm happy to discuss the detail behind this with you directly anytime. I have done much since, and stand behind the fact the chamber really doesn't burn that well. It does have some nice flow characteristics (it's effectively a bi-hemi chamber), and I can back that up with flow numbers some I have already posted link below, and will add the 3ltr head numbers when I get the chance to write it all up. Going back to one of your other questions, this should allow you to asses your intake / runner questions. I do have the volumes, and port velocity probe data taken at 10" depression. DCUK Martin kindly pointed me to some of the threads here; I don't tend to switch about too many forums as my time is some what challenged.

http://www.renaultalpineownersclub.c...t=5612&start=0
http://www.renaultalpineownersclub.c...pic.php?t=4899

I started the thread to share knowledge, but sadly have found it sounds a bit like me talking to myself more than anything else... pity.. Lots more I can put up there and will do in time, noting the intention hadn't been to push the parts (cams etc - cnc ground and have the files, so happy to share cam cards) I have developed for myself over the years, but to help others not go down the blind alleys I have done. The rocker ratio isn't exactly 1.5:1 as it varies as the cam sweeps the follower, and there are issues with the geometry and cam profile to get symmetrical lift profiles from 1-3 to 4-6. I want to do a roller rocker profile, as I believe this is really the way to go, but as a development cam from billet is going to be very expensive makes it prohibitive for just one set; noting you can't use a chilled cast as I do normally given the contact pressures encountered. So if this is something you wanted to get involved to reduce costs through scale, then let me know. There is a roller rocker that gives approx ratio of 1.6:1 that suits the hardware, so that makes a great start.

The ports and runner lengths are the same bank to bank on all the variants of the engine. The subtleties on the cams is the relationship of the rocker arm orientation to the cam lobe - leading and lagging effectively if you can picture my meaning. This results from the head casting actually not being handed, they share the same core casting, and just the external cast detail is handed. Hence you will see that on one side the exhaust ports face forward, and on the other bank they face to the back of the engine.... The cast cam blank and profile can be used either in an even or odd fire engine. The factory data isn't well specified for cam timing, and I have digitised most profiles, and none of the OE profiles I have tested are equal 1-3 to 4-6.

To get squish in the chamber the heads need to be welded. The piston crown comes to the top of the liner in all cases. I have skimmed the heads to the point of getting flat land area to take advantage of flat top pistons, but it takes quite a bit of material removal to do it. In the majority of my builds I'm forced induction, so not as worried about it as n/a, as I gain mixture motion in other ways. Note the ports do not induce much swirl, and fuel wetting is an issue. Correct the 45 deg seat is much better in this regard, and this is part of the advantage of the 3ltr head in standard form. I have also tried 55 deg seats with special valves, and this was for a strip motor, not ideal on the road.

I wouldn't take the OE odd fire rods to 8200rpm, they will fail certainly from experience in forced induction applications, and the odd fire crank is chocolate.. even fire is much better in this regard. Depending the cam profile, ramp rates, and closing profile the OE springs really need consideration. If you want I can post up their characteristic curves.

Regards,
Martin

[MFaulks]

Thank you. It's always amazed me when people who don't have any answers insist on chiming in without any constructive or factual input whatsoever, and the "moderation" here allows the resulting destructive chaos to stand, repeatedly. I will be speaking to you very soon and I think you may be interested in some of my recent projects. I seriously appreciate your willingness to openly share and look forward to one day making your acquaintance.

I will indeed take you up on the offer as I would like to get some serious software on top of what appears to me to be a thoroughbred choked down by some of the worst of EPA mandated malarkey, as well as some very poor design choices.

I recently made a batch of rockers with rollers on each end, they ride on needles and plan on doing some oiling modifications. You know what else has to happen to make use of them as well. That is in the works and i suspect it may take a few stabs to fully exploit the small port long rod geometry while conserving as much energy as possible.
I'm certainly interested in the possibility of a cooperative project and I sure won't buy anything from any supplier that finds it "distasteful" to merely post performance product specs, and I mean EVER.

The dual axis poly hemi seems to completely lack ANY squish whatsoever and that is a huge, but looks correctable, flaw in my humble opinion.

Have you run this chamber with tightly squishing (20 thou or so with Silovlites) flattops? I think that will be my approach and I'm going to do a bit reshaping on the chambers to make it worthwhile. The 30 degree seats are silly and I'll dig back and review where I saw discussion on the valve head shapes, intuitively, I want a 30-32 degree tulip with modified chamber (partially tubbed) although it is very possible that 20-26 degree may end up doing the serious business.

Hi Earl,

Thanks for the reply, and yes I would be very interested in talking about your recent projects. I'm easy enough to find on email or via LinkedIn, any way open offer. The rocker arms sound excellent, and something I would be interested in. There is an OE roller rocker from another Renault engine that fits straight in with the correct geometry (roller on the cam, standard valve end mushroom adjuster, and plain bearing for the shaft interface). It really beats me why no one has ever used it to upgrade a PRV. I have wanted too for several years, have the parts, but just couldn't get any of the UK cam manufactures interested to do a one-off billet with a suitable profile to test it - real pity. You are much more blessed in the US in that regard in terms of getting reasonable cost one-off development work done; noting I can't completely ignore costs. But this does correlate with your comment about utilising gas column momentum more effectively and getting this moving, and then utilising this energy for improved cylinder filling i.e. get the valve out the way as quickly as possible, gain time-area integral, and combine with a shorter rod ratio to enhance the rate of change of depression.

I haven't run less than 35 thou clearance, it would be better tight, just not tried it. I do on my Fiat SOHC engines, but they are my real passion I must admit. The chamber does actually quite a nice job of pressure recovery post inlet valve, and from that aspect I like it. But it does give up much in chamber surface area, open deck with no squish and little in the way of mixture motion control. So yes it would be great to do some heads with welded chambers. Have thought about it many times, but not been down that avenue thus far. Certainly on my flow tests, the flatter back valve has been on the money, but it depends on a number of factors as you know. However, saying that, I haven't done the flowbench to dyno full circle with A to B, B to A tightly controlled and documented tests to prove it outright. I would if I could afford both the time and money however. When I started on these engines out of a hobby interest, there was no one I could find to give me (or willing) any real data / advice, and consequently gained knowledge through trials, examination, and mistakes. Pity really as we would all benefit if people shared more.

Kind regards,
Martin

[EarlHickey]

message sent and cheers.....

Hi Earl,

Thanks for the reply, and yes I would be very interested in talking about your recent projects. I'm easy enough to find on email or via LinkedIn, any way open offer. The rocker arms sound excellent, and something I would be interested in. There is an OE roller rocker from another Renault engine that fits straight in with the correct geometry (roller on the cam, standard valve end mushroom adjuster, and plain bearing for the shaft interface). It really beats me why no one has ever used it to upgrade a PRV. I have wanted too for several years, have the parts, but just couldn't get any of the UK cam manufactures interested to do a one-off billet with a suitable profile to test it - real pity. You are much more blessed in the US in that regard in terms of getting reasonable cost one-off development work done; noting I can't completely ignore costs. But this does correlate with your comment about utilising gas column momentum more effectively and getting this moving, and then utilising this energy for improved cylinder filling i.e. get the valve out the way as quickly as possible, gain time-area integral, and combine with a shorter rod ratio to enhance the rate of change of depression.

I haven't run less than 35 thou clearance, it would be better tight, just not tried it. I do on my Fiat SOHC engines, but they are my real passion I must admit. The chamber does actually quite a nice job of pressure recovery post inlet valve, and from that aspect I like it. But it does give up much in chamber surface area, open deck with no squish and little in the way of mixture motion control. So yes it would be great to do some heads with welded chambers. Have thought about it many times, but not been down that avenue thus far. Certainly on my flow tests, the flatter back valve has been on the money, but it depends on a number of factors as you know. However, saying that, I haven't done the flowbench to dyno full circle with A to B, B to A tightly controlled and documented tests to prove it outright. I would if I could afford both the time and money however. When I started on these engines out of a hobby interest, there was no one I could find to give me (or willing) any real data / advice, and consequently gained knowledge through trials, examination, and mistakes. Pity really as we would all benefit if people shared more.

Kind regards,
Martin