Cyphear

I took off my stock GSR IM and put on a skunk2 intake manifold and it seems to be running a little richer everywhere (~.5 AFR -- I have a wideband in my car 24/7). I am happy with the manifold, but this would make me think it's flowing a little less air.

FWIW, I haven't reved it past 7,500 yet. I did unhook my wideband and rehook it up (possibly a difference in calibration...?? unlikey), but other than that I changed nothing.

I am definitely going to keep it on there because it's about 10lbs lighter than stock, much smaller (much more room to work), and much sexier, but I thought this was very interesting so I was curious what you guys thought.

redflaredcrx90

there is going to be a change in af cause you now have a manifold that flows twice as much air than your stock. less restriction ,you should be ok and you ecu will make the ness. corections on it own. to get full potential get tunned

LightningTeg

Your losing flow down low. Im sure it will be leaner up top. Do some pulls and log it and you'll see.

jarvis199

yea, tune that thing maiyne

Cyphear

Jarvis, I'm not sure what you guys are saying by getting it tuned. I obviously don't have a wideband in my car just for show.

redflaredcrx90, if it was flower more air, why is it richer?

My point is that it's richer and it should be leaner. I realize I need to lean it out.

I've done highway pulls and watched it. It's richer everywhere. I was expecting it to be leaner under boost, but it's not. I've tried pulls at 7lbs and 15lbs.

HamiltonRex

you should have gone with a good smim if your going to upgrade, or atleast an edelbrock unit.

Cyphear

What's a SMIM?

From the dyno's i've seen, the skunk2 outperforms the edelbrock until 7k. Since this is a street car midrange is very important to me (I am usually boosting it from around 4-6k, not 7k+ on the street -- plus it's a 84mm LS bottom end with a stock GSR head, which isn't a good recipe for high revs). Anyway, that was my logic in purchasing the skunk2. I can always upgrade to a edelbrock if I want a higher HP car, but right now I'm just making it a fast daily driver (400whp).

Even Jeff Evans (in my eyes, the most knowledgeable honda builder) says the Skunk2 is acceptable up to 600whp: http://articles.evans-tuning.com/200...rt-charts/#500

jarvis199

sorry i didnt mean to offend, but i know a lot of people who put widebands in their cars because people tell them to and they dunno what they are looking at...

youve most likely LOST some low-mid, and you havent revved it far enough to see where youve gained! datalog a wot pull and ill bet the afr's up top are leaner...

ive also seen setups that want less fuel when they become more efficient, so keep that in mind...

Cyphear

No problem. Mine is not for show. Nothing on my car is!

I will try to take a closer look at it, but i'm pretty sure I got a good look at it yesterday. I don't have any dyno graphs or data logs to compare it to, so I'll never know for sure if I gained or lost power, but I am pretty sure I remember it being leaner. I was doing some highway pulls and when I let off it was 10.1:1 at one point. I definitely wouldn't let my car run that rich. Granted, I am happy anywhere in the 11's (I like to run it a bit rich for safety), or even dips in the high 10's, but 10.1:1 is RICH.

It'd be nice if it was more efficient, but I can't think of any way richer would equate to efficiency. If it was getting more air or a better burn, it'd be leaner. The fueling obviously hasn't changed. I deifnitely could be wrong though, so I am curious. Under what circumstances have you seen a car need less fuel?

jarvis199

any chance its reading in an untuned part of the map? like say u were running 9 psi before, maybe somehow its making 11 now and its richer there?

well, actually, just today i retuned an NA d16a6 crx with p29's and a bisi cam. last time itw as tuned was on the dyno, it made the most power right at 12.8:1 afr, but after putting the bisi header on it, it dropped to high 11's and low 12's! dont ask me why lol, but it made 16 whp more on the bisi compared to the ebay header!

Tjabo

Is your boost level the same when doing these pulls as it was before? It's possible that a better flowing IM might cause your boost to have dropped a little bit depending on how you're regulating it, which could cause you to be operating in a slightly different area of the map. After all, boost pressure is partially an indication of restriction in the system backing up the air flow the compressor is trying to ram through.

Just a thought about how this could happen, even if the IM is flowing better/more efficiently. . .

Cyphear

The boost controller is set the same, but you bring up a good point Tjabo. It's definitely the same within a lb or two. I run it at 38% (~14lbs) on the street a lot (i've probably had it set there for 90% of the last four or five years), but it could be a lb or two different. I suppose it's also possible that the placement of the vacuum nipples is different (better) on the Skunk2, so my ECU is reading comparatively more boost and spraying more fuel.

That's a great example Jarvis, but I still have no idea why. I guess it's good to hear that this isn't completely abnormal, but I am still a bit curious. It seems to be running strong. I can't say it feels any faster or slower, but it's definitely not running bad. I'm not too concerned, I'm more curious than anything.

To me, it basically means that either the mixture is burning differently, or the MAP sensor is reading a higher pressure compared to what's getting into the motor than it did before, and neither of those seem very plausible to me.

Tjabo

So you're seeing the same boost pressure on your gauge now as you were with the other IM?

Cyphear

yeah. It's not like I memorized the exact boost level at every RPM, but for the most part it's the same.