what does a rich misfire feel and sound like?

[ADAM]

i think i am getting a rich misfire around 3-4k rpm....the motor bogs down and kinda goes...woh woh woh woh woh...it only happens if i pick a high gear and go to WOT at a low rpm?

if i am in a low gear and go to WOT it does not happen?

[ADAM]

i figured it out...its actually called compressor surge, its a unstable region of the turbo compressor due to lack of air flow...its because i chose a turbo compressor that really only works from 4000-6000rpm below that it really starts to surge and does not work to well...

FYI i choose this compressor due to the very high efficiency at high boost levels and high rpm (over 74% efficient) so it generates little excess heat at high rpm and high boost..downside is..it does not work at all at low rpm and partial throttle....(which on the race track is not an issue since i am always above 4000rpm) but on the street cruising on the highway it does come up cause you can easily be in 4th or 5th at sub 3000rpm levels and floor it...only to have this turbo surge happen and ruin all the fun..

[toadee23]

Compressor surge is bad bad bad for your turbo man, what kindve turbo are you running anyhow? I judge from your other posts you're driving a s13 or 14 240sx with a turbo'd ka24de? (thats your first problem, you shouldve gone with the sr20det, EVERYTHING about that motor is more performance oriented, more durable, and just plain better than the ka24 junk, but I digress...).

Youd probobly be faster with a smaller, properly matched turbo anyhow. Not much smaller, Im guessing, but lagging to 4000 is unacceptable unless you highway race a Supra. IHI, Incon, and FP all make really great low lag turbo's....

However, since turbo'ing the KA24 is a bad idea anyway, I'm not sure what Id suggest, youd have many more options and support with the SR20DET (as well as a much better manufactured engine).

Also, since I don't know how much work youve done to the internals, as much porting you can afford is advised to at least alleviate some compressor surge. Port port port, especially on the exhaust side, anything you can do to get that impeller turning the compressor side faster is great. No cats would be a big help (seeing as how you're running so damn rich its not even funny Id be surprised if you have much of them left anyhow).

[ADAM]

yeah its bad for the turbo...but 74% efficiency is worth the effort, since i am only interested in high revs..just have to stay away from WOT at less than 60% of my rpm range thats all...

he he... SR20det vs the KAT battle...its a big one for nissans...but in most of the cases..the KAT's have held together better, and have much more torque than the SR's..we 240sx guys constantly battle about this....so its been mulled over 100's of times already..sr20's are just the most recent hype..the ka block is much stronger..as for being better built...nope...but thats another battle

not having any lag issues..its not spool up thats the issue..its surge...

using a h3 cheetah compressor in a t4 housing..typically used in upgraded GN's

plus i am using a half ass fuel computer right now..which is soon to be corrected...