Hi All Here's a collection of points written by Darren in response to mails I forwarded to him off the DML, and general chatting with regards the PRV hunting. There's some other info in there about how to set up the fuelling, and also a reply to Bill identifying his engine. I hope it's interesting and not _too_ long. Martin #1458 #4426 --------- My opinions will probably keep the guys across the pond "cussing" for ages! At the end of the day I know what works and when I build an engine it has to run perfectly, and they always do, or else a running fault could cause premature wear of the new engine (probably the reason the engine wore out in the first place). Many of these guys with opinions have cars that hunt......That is the case for the defence your Honour :-) Shain makes the most sense. I am beginning to believe it is a problem with vacuum leaks; perhaps we are getting too deeply into the fault and it is nothing more than 20yr old rubber O rings are no longer sealing properly when cold. I know that when I strip a PRV the inlet manifold O rings are squashed and turned from rubber to hard plastic. To the guy who suggests disregarding the Renault manual; the Renault k-jet manual is written by Bosch and it does cover Lambda vehicles (Switzerland) as it is written for european vehicles but I can see how he comes up with that idea not having seen the Renault manual. There is no way a variation in cylinder pressures or spark plug variations would cause an engine to hunt, in fact one running on 5 cyls would not hunt, it would idle slower which would then be corrected by the idle valve and then held steady by the valve if set up correctly. I suspect that even someone who has been working on DMC's for years would not know the correct setting proceedure as it is not in the DMC manual and they would be unlikely to get hold of a Renault manual as Renaults are not sold in the US. It appears that DMC didn't want unskilled people messing with the settings but Renault had no proplems with giving the dealers the info to set them up. To set the idle you clamp off the pipe to the idle valve and set it with the brass screws as per engines without idle system, ie remove and clean the screws, refit them and screw them all the way in. Back off the two front ones 2 turns and then set the idle with the back screw to 900 rpm. It is absolutely critical that the control pressure is correct (3.4 bar) and that the pressure from the pump is correct (4.8-5.2 bar). The only thing you can't do on the DMC is set the co which should be 0.7-1.0 before the cat. The idle should not vary when cold and the manual gives all the testing proceedures and values of electrical sensors etc. A simple way to set the mixture screw with out a co meter is to bridge the fuel pump relay with the engine off, pull out an injector and put it into a container and put a washer (about 0.5mm-1.0 mm thick) under the air plate stop to hold it in the same position as at idle and turn the mixture screw untill the injector "cracks" which is the point at which the injector starts to spray. Then set the idle... The K-jet system will handle more than 140 hp,the standard Volvo 760 is 170 hp in european spec without cats. The Renault 5 Turbo 2 (mid engined) used the PRV metering head and produced upto 350hp from 1400cc in tarmac rally spec! I also used to prepare a Golf GTi 1.8 with K-jet that put out 190hp, although the idle had to be set at 2000rpm because at low speed the pulses that came back up the inlet manifold upset the flow plate, that is the only problem with k-jet when the cams get wild. The pulses push the flap shut as the pulses going in are trying to push it open when you run cams with alot of valve overlap resulting in no air movement which equals no or very poor idle. Obviously the active idle speed valve was not designed to operate with toblerone shaped cams with big overlap, it was designed to give a steady idle dependent of engine load with standard cams. ------- (Bill's engine) Ah, The Renault 30TX is alive and well and living in a DMC! The injection system Bill describes is Phase 2 R30TX. I have actually got a factory bulletin from Renault advising how to retro-fit this system to a phase 1 30tx that has running faults (phase 1 had the same as DMC). The metering head is alloy, not cast iron, the fuel lines are solid steel pipe and it has a conventional fuel pressure reg as well as a k-jet pressure reg to improve throttle response. As to a lack of power, it should produce more power, as in the Renault it gives 144bhp from a 2664cc PRV. The lack of power could be down to the distributor not giving enough advance if it has a DMC dizzy.If he wants a Renault dizzy I have them in stock, but he needs to get the advance checked first. The supplied engine number for Bill show 140 which is a Renault 30TX engine out of a phase 2. It may lack torque off the line as it is only 2664cc! Sounds like he needs an engine building to 2849cc..... -------------------------------------------------------------------- mail2web - Check your email from the web at http://mail2web.com/ .