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Helping a buddy out here, recently had his car at a very reputable tuner after a fresh motor build.
440 LSX
Ported RHS LS7 heads
Ported MSD Intake
251/269 .675/.675 114* cam
NW 102 TB
Fast 85lb Injectors
LS7 Map and LS3/7 MAF
Stock fuel system with BAP
Issue is at 3500 the car just dies for a second, then recovers and pulls.
Tuner is saying change injectors and throttle body. I have a NW 102 on my car so I doubt that's in, but 85 lb/hr injectors I think are too much for 600-650 RWHP N/A (I was at a acceptable duty cycle on my TT car at 760 RWHP on a TT setup). I think the injectors might be the culprit as the fueling is going into PE but I'm no expert. Thought I'd query some minds here. I can't see it being anything mechanical as it would most likely present issues before/after 3500 RPM also.
I have a HP Tuners datalog but don't have HPT myself if anyone wants to see it.
It was a tailpipe wideband on the dyno to my knowledge, but you can see the Bank2 spike lean via the O2 sensor voltage tanking down to 43mv at it's worst. Happens at 10:33:55:9xx is the start point in the log.
Bank 1 starts to do the same thing.. it drops down to about 700mV (from ~900mV) but as you saw bank 2 goes further lean that 1. The wideband agrees that it going quite lean in that spot.. Injector PW, WB and NB O2's all agree as well. The WB dip is a bit delayed from the NB, which is to be expected.
I'd need to see the tune to be sure but the obvious fix would be tweaking the MAF or VE tables depending on how it's setup (probably MAF only, looks like that is all it' using).
There's also some major knock happening not long after the lean spike.. so I'd do some timing tweaks at the same time as the MAF/VE tweaks. That KR looks pretty real to me the way it happens then starts to fall then happens again, and again
Overall, looks like the tune needs some work. This is stuff any tuner shouldn't have any trouble fixing.
I wasn't there for the tuner who was doing this but he's a pretty prevalent guy in Indy. From what my buddy says he was trying all sorts of stuff but nothing was improving at that particular location in each pull. I can try to get the tune file but I don't think that's gonna happen.
Gotcha. I wasn't there (obviously) so I have no idea what's been tried.
Only other possibility (aside from obvious changes to MAF table) I can think of is some sort of misfire? That will show up as a lean spike. But that happening on both banks at the same time seems like a long shot?
Injector PW seems to go up pretty quick right after that lean spot but is flat right at it.
Glad to see I wasn't off with my suggestions to this on Facebook. I suggested to get the tuner to throw a bunch fuel in right there to see if it reacts, or to tune it in SD and see if the same thing happens.
He also stated that the car doesn't start or idle well so I'm pretty convinced that the tune just needs work.
Glad to see I wasn't off with my suggestions to this on Facebook. I suggested to get the tuner to throw a bunch fuel in right there to see if it reacts, or to tune it in SD and see if the same thing happens.
He also stated that the car doesn't start or idle well so I'm pretty convinced that the tune just needs work.
Totally agree about it not starting or idling well. The log reflected that because I was watching it on real time thinking "my god this needs open loop and startup work."
I CAN get the tune file at this point if someone wants to look.
The owner emailed me the tune last night...and I have to say it looks like a bit of a rush job to me and may need some work.
I made a few notes and sent them to the owner.
I'd be interested to see if we pick up on the same stuff, cause you have a good eye for this stuff and I'm still trying to learn about some things.
I'll send you the list of notes I made via email if that's alright just to compare.
That peek power and torque seems WAY low compared to what I would think for that setup. Unless they kept working past that point and didnt just give up after 2 pulls.
I would think with that setup HP should be close to 600whp and torque should be 530-550.
Im just comparing that to what I made on my setup which is a LOT smaller than that on almost all counts(except maybe the heads, dont know what RHS head work flows).
That peek power and torque seems WAY low compared to what I would think for that setup. Unless they kept working past that point and didnt just give up after 2 pulls.
I would think with that setup HP should be close to 600whp and torque should be 530-550.
Im just comparing that to what I made on my setup which is a LOT smaller than that on almost all counts(except maybe the heads, dont know what RHS head work flows).
I agree. The owner understood that it was low on power because the tuner didn't want to go forward past this issue, but I hope he can get it lined out. I sent him a few things that I found from the tune that could probably be corrected (maybe schpenxel did as well) so hopefully he can get it through and get this setup working like it should.
04-15-2016, 07:11 PM
WEIRD dip in dyno graph
