steven975

I got my Stage 1 SOS Supercharger installed last week, and this is the result of the first dyno test.

I had been taking it easy on this thing, and not pushing it to over 7500RPM until I had it dyno'd...good thing.

The AFR is spiking to 12.3+ (tuner let off at that point) after 7200RPM or so. It's not REALLY high, but it's not doing what it's supposed to be doing (the AFR should be DEcreasing as it hits boost). Due to this, we decided not to take it beyond that point.

Still, it is making 238rwhp at 7100RPM You can see the torque is falling as it leans out, though.

Soooo, I have not had the injectors cleaned and rebalanced as SOS strongly recommended (car is at 73K miles), so it does look like I need to do that, huh?

We turned up the fuel pressure 2 turns, and off boost it runs down in the 8-9AFR (way too rich), and then once it hits boost it's leaning out. It's supposed to richen up as the boost/RPM increase. The tuner and I both think the injectors are not able to put out enough fuel, and cleaning the injectors and/or fuel rail seems to be the way to go.


The car is a 2002, 72K, CT Exhaust, SOS SC kit Stage 1 6psi. Temp today was 85-90F

Baseline dyno (100% stock) is here:

https://www.s2ki.com/s2000/uploads/g...106_966716.jpg

Today's dyno is here:

s2000Junky

Something isn’t adding up. I don’t think your problem is with your injectors needing cleaning or not functioning properly. You should not be seeing 8-9afr out of boost, something is wrong there and it doesn’t sound injector related. Your stock ecu compensates for any added fuel pressure at idle/part throttle (closed loop) 12.3 afr is typical for your set up and not too lean btw. I would be curious to see what the rest of your afr looked like if you did a full pull. Typical fuel pressure at idle with your set up is about 50-60psi. The black piggy back box they incorporate in their kit is a map clamp, vtec control(lowers) and some fuel correction. The rising rate frp is the primary fuel lean/enrichment component, but only comes into effect when boost is present. So if your getting an overly rich condition outside of this, then you need to figure this issue, maybe something isn’t hooked up right?

steven975

Before we adjusted the FPR, it was running where it should (~13:1 AFR at lower RPMs and falling as RPMs climbed...until the spike). We had turned up the fuel pressure on the FPR...and that is why it was so low (rich) before hitting the boost (it was a troubleshooting step to try to decrease the AFR up high). But the AFR still spiked even after increasing the fuel pressure. While I agree 12.3:1 or so is not really lean, it should be BELOW 12:1 after 4500RPM and approaching 11:1 at redline. While I'm sure my engine won't blow up on the dyno at 12.5:1, I'd rather not risk it and fix this.

I've since turned the FPR down to where it was stock as that ratio was better/optimal for the idle-7K range I'm going to keep it in until I figure this out. Even at that, I'm ~50whp over stock so I can live with it for a few weeks.

SOS believes it is either the injectors (they are not spitting out enough fuel, hence the leaning out when there's an increased demand for fuel) or the FVM (Fuel/VTEC/MAP) module. They heavily recommend having the injectors cleaned in their directions, and I think that's a good first step.

They had me diagnose the FVM to make sure it was working by testing the VTEC engagement, and it's right where it should be at ~4700RPM at full throttle. The FVM module is clamping MAP voltage, too, as the max vaccum/boost is 0psi read from the ECU via the OBD2 plug.

I'm also going to order a fuel pressure gauge. Another possibility is the fuel pump being weak (Walbro 255) but I hear that's rare.

Moddiction

SO what were the AFR's leaning out to at redline? 12.3 sounds perfectly fine and normal. Anything under 13 really is ok for a bolt on supercharger kit. Mid 12's would be better though or low 12's ideally imo.
Mid 12's at redline is fine and probably how the kit was made. Sounds like nothing is wrong with it but you are just nervous of the afr's the kit is made to work at.
I'd just get aem ems or similar if your worried and get a full tune.

steven975

Yea, an AEM EMS (or Hondata, if I feel like spending extra AND pulling the crank pulley again) is in the future plans along with more boost and injectors...after a clutch and a top (going blue!). I'd say 6-9+ months out.

I haven't taken it to redline yet, so I don't really know if it'll spike into the 13s or not. The most I've done is 7500 or so.

You're right, I'm probably just nervous Still, I want to do it right. SOS told me that RC has a very fast turnaround, so I'm going to send the injectors off for cleaning or get some stockers from ebay/here and send those off.

Anyone know if the B&M linked in the FAQs has enough clearance for the hood to close and not break the gauge leaking fuel everywhere? Any recommendations for a fuel pressure gauge that isn't intrusive and can possibly be moved to the interior at some point (though I REALLY don't want to go the Fast&Furious route with a gauge pod)?

Moddiction

12.3 is nothing at all to be worried about. Have it revved higher and see what happens. You are just going to be wasting money sending injectors out to be cleaned I think.
12.3 around there is completely normal and where you should be at!

steven975

Also, the AFR is being measured at the tail...would that yield a slightly leaner ratio than if it were measured at the cat? I'm new to this so forgive me, but can the AFR be measured anywhere else on a stock ECU? It doesn't seem to be an output on the OBD port.

Cleaning the injectors is about $100-150, so it's really not much for peace of mind IMO.

Moddiction

People usually weld in a bung on the test pipe or header by cat and hook up a wideband sensor there.
I guess if you want to spend that to spend it but if you are still worried about the 12.3 afr knowing your injectors are clean won't ease your mind since it will still be there haha.
Just have them do a pull to redline and see where it's at. If you see it lean over like 13.5 I would stop. Hell I ran mine at 15.5 or so afr and it didn't blow lol.

steven975

Thanks...I do appreciate the feedback.

If the cleaning the injectors don't fix it and it still only spikes to ~12.3 I'll take it higher. 13.5 does seem like a good abort point...but no way would I do 15.5

SOS is saying that it's not supposed to start running leaner in boost...the AFR curve they show with the directions has a slight negative slope from 4.5-8.5K at 11.7 or so, with a larger drop to ~11.3 from 8.5-9K. SOS did have it in their directions to clean and flow-test the injectors if past 60K, and I'm one to follow directions when spending $5K+ when I'm no expert on what I'm doing. While I have an OH$HIT fund, I'd rather not spend it this week on a new block

Yea, I'm overly cautious...probably makes me look like a wimp

Moddiction

It always runs leaner when it hits vtec and then richens up a little bit towards redline. From my experience atleast.