The way i see it is if the curve is wrong [ie too much advance down low] and/or the base timing is abit higher then it should be, then it will cause rough running and sluggishness, for example at big throttle openings at low engine speeds.
You know your car better then i do/you know what you have or havent checked, just a suggestion
I think it's a good suggestion, and I guess it's all the impetus I need to install the Kameari distributor system. I haven't done it yet because it'll need the oil pump to be dropped, but it'll give me a chance to measure the oil pump for wear, and you never know, the distributor might make the problems go away....
Well....some ppl have suggested that the engine problem may be compression-related, so I dug out the compression tester and gave it a whirl and....
....the readings are all very high! 190~200psi. This is the same gauge that I've always had and after I had my MX5 engine rebuilt with 10.5:1 comp it read 205~210psi, so the gauge is reasonably accurate.
Now, what I was expecting was that if the cam timing was way off, then the readings would be super low from the valves opening too early on the compression stroke....but these are very high readings for something with an allegedly big cam...
But it's a massive relief that the engine isn't rooted, and I presume it's as freshly built as the head is. Hmm...I am starting to think maybe it's an ignition issue instead....
Anyway I moved on and decided to re-lower the car
For rego, I'd installed these tall King springs which gave the car 16cm of ground clearance
I only needed 10cm but decided it didn't hurt to overkill it.
As before, to remove the springs, you undo the shock and the driveshaft and the control arm will swing down enough to remove the spring.
When I first got the car it was so low that it was sitting on the bumpstops, and so I got these shorter bumpstops from GTR specialists http://www.protec-s20.co.jp/
when I was in Japan...as you can see they are 40mm shorter than the stock ones.
But are they TOO short?
I compressed the shock by hand, and the masking tape marks where the shock bottoms out. As you can see, when I push the suspension up to its bump limits, the shock is bottomed out...
...the tyre is actually jammed against the top of the wheelhouse
...and the fancy JDM bumpstop isn't even touching yet!
The solution seems to be to space the bumpstop out, so that it's not a whole 40mm shorter, but only 15mm shorter than stock...
At that point there is still 30mm of shock travel left...
...and about an inch and a bit before the tyre starts to remove parts of the bodywork.
This is rather bizarre...the bumpstops are definitely the right part, and I'm pretty sure there isn't some special spacer or anything that I was supposed to buy as well. Just goes to show you should check new parts before fitting them up...I guess it's possible that a real GT-R has a deeper wheelhouse so you can go lower?
I'll seek out some proper 25mm spacers and longer bolts tomorrow and that should get the new bumpstops sorted.
No Kev, you are eating a duck fetus.