jagman Posted April 25, 2005 Share Posted April 25, 2005 we have now rebuilt and refitted CJs engine,he is now running in the engine,the results look promising ; the effect so far with the ported and polished head is a reduction in egt of 100 degrees c under the same conditions as prior to his plug fail, I did promise pics,but havent got round to it,as my head comes back this week I will take some pics of mine post porting. As the engine is run in and running more boost we will get more feedback on the egt margins and the effect on spooling of the single turbo I will post more later Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted April 25, 2005 Share Posted April 25, 2005 Adam how have you measured the EGT's when the car is being run in, so therefore I assume off boost or very little boost??? Quote Link to comment Share on other sites More sharing options...
dude Posted April 25, 2005 Share Posted April 25, 2005 Adam how have you measured the EGT's when the car is being run in, so therefore I assume off boost or very little boost??? Hopefully Dude :littled: Quote Link to comment Share on other sites More sharing options...
dude Posted April 25, 2005 Share Posted April 25, 2005 What we need is a dyno before and after , TBH the sup head is very good to start with so IMO not very good bang per $$$$ Dude Quote Link to comment Share on other sites More sharing options...
JohnA Posted April 26, 2005 Share Posted April 26, 2005 I've been reading on an american site some 'expert' modifying sup heads to fix the 'issue' with the offset inlet ports. He thinks they're a weak link, a defect of some sort, which he felt should be put right. Oh dear these people have hundreds of nukes too... Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 26, 2005 Share Posted April 26, 2005 So what's the mechanism at work here? 100degC reduction in EGTs from porting and polishing - that must be almost a 10% drop? Or am I missing the point? Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted April 26, 2005 Share Posted April 26, 2005 John, who was it, some of the US guys are very clued up with the 2JZ. Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted April 26, 2005 Share Posted April 26, 2005 So what's the mechanism at work here? 100degC reduction in EGTs from porting and polishing - that must be almost a 10% drop? Or am I missing the point? also in a car that is being run in, off boost, kept below 4k. Would be good to know at what load point the comparison was taken. Quote Link to comment Share on other sites More sharing options...
JohnA Posted April 26, 2005 Share Posted April 26, 2005 So what's the mechanism at work here? 100degC reduction in EGTs from porting and polishing I think it's highly unlikely mate. If the figures are correct, then he's probably not comparing like with like. This happens often, as after the headwork, other things are also changed, sometimes cam timing, even the turbos (and a different exh A/R or wheel size will affect EGTs big time...) Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 26, 2005 Share Posted April 26, 2005 That's why I said am i missing the point. The first post reads as if the porting and polishing is being credited with the drop in EGTs, but maybe I'm reading it wrong. So apart from the head, what else has been changed? Quote Link to comment Share on other sites More sharing options...
Alex Posted April 26, 2005 Share Posted April 26, 2005 Additional things to consider. Different map? Different (oversized) valves due to it being a valve that melted to cause the issue. Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted April 26, 2005 Share Posted April 26, 2005 That's why I said am i missing the point. The first post reads as if the porting and polishing is being credited with the drop in EGTs, but maybe I'm reading it wrong. So apart from the head, what else has been changed? That is how I read it too Quote Link to comment Share on other sites More sharing options...
CJ Posted April 26, 2005 Share Posted April 26, 2005 TBH, this may have been my fault for not explaining things to Adam properly. I will give an update when the engine has been run in and I can give it some welly As for the changes, it has had the following: 2mm HG New oversize valves New Ti springs and retainers Polished and ported head ARP rod and head bolts New Pistons and rings All cylinders honed New BL auto box New shroud fitted around the FMIC to ensure maximum air throughput I have probably forgotten something Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 26, 2005 Share Posted April 26, 2005 rods???!! nice spec tho CJ. Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 26, 2005 Share Posted April 26, 2005 Lower compression ratio and better intercooling, then? Quote Link to comment Share on other sites More sharing options...
CJ Posted April 26, 2005 Share Posted April 26, 2005 rods???!! nice spec tho CJ. I asked the engine builders to check out the existing ones and they said they were fine and dandy. Bear in mind that I will not be trying to reach eleventy hundred BHP - unlike some who push the boat out Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 26, 2005 Share Posted April 26, 2005 New valves=new seats=affect valves ability of heat transfer. Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 26, 2005 Share Posted April 26, 2005 Cool CJ, whatever floats ur boat. Quote Link to comment Share on other sites More sharing options...
CJ Posted April 26, 2005 Share Posted April 26, 2005 Lower compression ratio and better intercooling, then? Unfortunately Digsy old bean, my technical knowledge was exhausted in the first post I made in this thread Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 26, 2005 Share Posted April 26, 2005 ...and what Usamann said. Any idea how much bigger the valves are over stock? Quote Link to comment Share on other sites More sharing options...
Alex Posted April 26, 2005 Share Posted April 26, 2005 They'll be 1mm oversized as I think that's all you can get Quote Link to comment Share on other sites More sharing options...
Digsy Posted April 26, 2005 Share Posted April 26, 2005 ...and what's the stock exhaust valve seat diameter? (Which is what I should have asked earlier - doh). Quote Link to comment Share on other sites More sharing options...
CJ Posted April 26, 2005 Share Posted April 26, 2005 They'll be 1mm oversized as I think that's all you can get Correctamundo Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 26, 2005 Share Posted April 26, 2005 AFAIK, the porting actually decreaces the rough surfaces in the head, the casting so to speak, the rough surface actually decreaces the surface area, which is relative to heat transfer, that is my understanding behind it. But with high HP apps, you want air in and out as AFAP. Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 26, 2005 Share Posted April 26, 2005 Stock exhaust seat is between 1.2-1.6mm Quote Link to comment Share on other sites More sharing options...
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