Thread: SR20VE+T low on power, please help!

The more I read this (especially ca18's post above) - starting to think something is wrong with your motor. If that's the case, hopefully it is just a skipped tooth on the chain or something.

No I haven't checked all the grounds, there may well be a dodgy ground somewhere. Though nothing has changed and the car dynoed perfectly just two weeks prior when it was na.



Hmm that's the opposite of what I've always heard. I thought the idea was to leave the switch points fairly high when small turbo and then put them down below 4000 when you had a big turbo and needed to try and spool it.
I just learnt some very interesting information using an online engine speed calculator however...the dip that occurs at 120km/h is at 4400rpm. No idea why it would be dying in the ass there but anyhoo I'll take the laptop outside now and change the switch points to be together at 4500 and see how it feels and also unplug them and see how it feels.
ALSO, what I thought was the 7800rpm limiter at 180km/h at the end of the graph is actually...6600rpm! Who knows what happened over the last 1200 revs!? Might have made another 100hp haha. But seriously, I need to get back on the dyno.
I made peak power at 5600rpm...that's messed up.



Mmm there's always been something funny about my motor...me and @kiwi-japie pulled the rocker cover off years ago because we suspected a skipped tooth, but no. It also idles perfectly and gets fantastic fuel economy, you'd think a skipped tooth would mess with that kind of thing.

If it was a skipped tooth, it would be on the intake, if it were the exhaust cam, you would have timing issues, and the car would damn near not start.

Yes and No.

Yes with a big turbo switching the Exhaust cam can result in better spool. Because with the inlet on the low lobe there is very little energy wasted in the chamber and it all trickles out the exhaust which spools the turbo. Add to that that the inlet cam is much more crucial in regards to over caming and turbo response. (there is a reason Nissan put vtc on the inlet only) also a reason many companies make staggered cams with the inlet smaller than the ex.

Your situation is still very different to this. Its about the efficiency of the turbo. You have a small turbo that can only flow soo much air.

So using your figure of 4400 is 120kph. Lets look at the graph.

120kph dip is 4400rpm
130kph the power curve rises again which is 4800rpm
153kph is peak power just before a dip which is 5600rpm
170kph the graph begins to rise again 6200rpm
180kpph car maxes out. 6600rpm

Also your boost starts dropping at 137kph right when your cams are switching. Its only 1psi not really a big deal.

So from 4400-4800 something is making the graph flatline. There are no real issues with your boost. Would love to see an a/f trace.

Thing is the car looks really strong up until 4400rpm. i.e you are making 190hp at 4400rpm on only 12 psi on small cams through a small turbo......that's a solid effort. I doubt there is anything wrong (hardware wise) with your engine.

Defiantly switch your cams at 4400 and see what happens and then look into the tune. The graph is too erratic to be dump pipe imo. You are running quite high comp and at 4400 you are on cams with no overlap. Switch the cams earlier and spend a bit on time on the tune and I reckon she'll be right. What base tune did you load?


P.S. a mate skipped a tooth 1 tooth adv on the intake and it still idled fine and drove well in the low rpm with good economy.

I would also check your dizzy.

Ahkay, yeah well like I said, it didn't when we originally suspected it years ago. Haven't swapped cams or done anything since, doesn't something have to go wrong for it to skip a tooth? Like an over-rev or some other screw up?



Yeah it's interesting how the boost drops exactly when the cams switch hey.
IIRC it was actually leaning out pretty hard to 12.6-8:1@4500. Did it on the way to the track in fourth a number of times, so when I got there I chucked more fuel into and got it back to 11.3:1-you'll see if you look at my fuel graph I've bumped the values to 140 from 4000-4800.
So that could be a big contributing factor to that first dip. The messed up curve after that though...

I set the cams to 4500 and when for a spin last night, unfortunately it had just rained a little so the roads were damp bum dyno got no accurate readings. Even in 4th gear though, as soon at it hit 4500 it started wheelspinning like mad. I think traction is gonna be worse now lol...it seems like it really shocks the power curve when the cams are switching. I'll go out again tonight though and get the MAF voltage reading and see how it feels if it's dry.

I just loaded my n/a tune and obviously adjusted for the injectors and put more fuel in. And then put timing at 10 degrees across the board haha.

Appreciate your help man

copy and paste all your logs.

TPS/MAF/timing/inj duty cycle everything you got.

Also, get compression results.

-G

Will do.

But for now: I beat the sti that I lost to when I started this thread so something is working.

Stock sti? Good job. Steps in the right direction

Thanks
But negative, 2012 model with 310hp atw. When he was making 275hp he went 108mph at the drags, so hopefully my car is pretty close to 110mph right now. Which I'd be fairly happy with.
Oh and after I beat him we raced off the line. It was funny.
Also, when the car is seeing nothing but vacuum and then I hit it in 2nd or 3rd and it goes straight to 11psi, the whole car jerks and it's at least a half second before I really get moving. Not beneficial for winning races
However when I raced sti the first time last night, we were going pretty slow in 2nd to start, maybe 3000rpm on board, so the car steadily boosted 5,6,7 then 11 by 3700 and there was no jerking and I just walked away from him. Which I enjoyed haha.

not bad. I believe the STI chassis is a bit heavier so beating one with 310 atw I'd give a rough guess you're probably around 285ish whp.