Smooth at 11.2:1 AFR, small hesitation at 11.0:1 AFR

[Spoolin92GSX]

To give a very small back story, I've had my DSM tuned to 11.2:1 WOT AFR for a few months and it's seemed pretty happy there on 91 pump gas. After a recent canyon run with a buddy on his R6, I noticed my manifold glowing a little and decided 11.2:1 is still a little lean (I unwittingly ran close to 12:1 before getting tuned and it glowed A LOT more).

So I went to tuning last night and got 11.0:1 pretty smooth all the way through the RPM range +/- 0.1:1. Here's my question - at 11.2:1 it would pull butter-smooth up to 6000RPMS (that's just as high as I rev right now), once I had 11.0:1 locked in, I can feel just the slightest hesitation during a 3rd gear pull.

Compression test was done a couple weeks ago with 150psi across all 4, brand new NGK plug wires, BR7ES's gapped to .028 with a few thousand miles on them, Walbro 255 rewired, AFPR, clipped 16g. I know there was 1 or 2 counts of knock but that was remedied with 1* of timing pulled from those cells, and I know my 450cc injectors are pegged, but the hesitation happens maybe around 60% duty cycle. I was going to attach a log, but TunerProRT's log files aren't supported.

 

[Boostdriven]

I looked at your mod list and it says you run 14psi, 11.0:1 is a little rich for 14 psi, you can safely run 11.5:1 also gap the plugs to about .023. Most of the heat that you are seeing on the manifold is not 100% related to your air/fuel ratios though it is a big part. The fact that you have stock cams, stock exhaust manifold and small stock exhaust housing have a lot to do with your egts being high. if you don't have an egt gauge you should get one, though you can't really tune much around it and some may say its a waste of money but I like to have one just to see how my car is running.

 

[Spoolin92GSX]

Yeah, it felt like 11:1 was a little rich.. That's a good point though about the exhaust; I have a carbide bit on its way and I'll be porting the hell out of the manifold, o2 housing, and possibly the turbo if I'm feeling brave. I actually have a Greddy EGT gauge sitting in a box that I got from a friend for free, I just have to get a new probe for it. I'll probably end up leaning it back out a tad until the hesitation goes away, I don't romp on the car that much anyways so it's not a HUGE concern. I've seen 16g's glow a LOT brighter than mine and last with no issues, so meh.

 

[Boostdriven]

If you can get your hands on a 2g manifold that might be a better option for you. If you are going to port the exhaust housing try opening the section where it funnels down right before exhaust hits the wheel, that section in those housing is kind of small. If you look inside the housing as it funnels down it comes to a point where exhaust starts to escape in to the wheel, if you port the section slightly up that will allow exhaust to escape from a larger diameter in the housing reducing your exhaust pressure a bit and lowering your egts. If you email me I'll reply with a picture so you can see what I'm talking about.

 

[spyderturbo007]

I wouldn't waste money on an EGT if I were you. You can end up with high EGTs from being rich or lean so it's no indication of your tune. I've seen people beat their head against the wall trying to tune using an EGT.

I would be careful going too lean on the stock 450's. Mathematically the 450s can support 32.3lbs/min at an IDC of 100% or 25.84lbs/min at an IDC of 80%. That's easily achievable with a 16g.

 

[Spoolin92GSX]

The main thing I'm focused on porting on the turbo is the step/lip on the inlet. The previous owner of the turbo had the turbine wheel clipped, so flow in that section shouldn't be an issue. The manifold and o2 housing on the other hand.. That's going to be some blood and sweat..

I won't be wasting much money on the EGT if I decide to run it, just grab a K-type thermocouple from eBay (it's the same damn thing) and if it doesn't work oh well. It'd be more for an idiot light when I'm on boost for long periods of time. I know I'm running these 450's to their ragged edge but I should have a line on some 680's soon here.

Thanks for the input guys, I'll probably leave it where it's at. It pulls great for 14psi and it's not blowing up

 

[spyderturbo007]

If you have the time and tools to do the porting, I would go for it. However, if it's going to cost you for tools or you're paying to have someone do the porting, save your money for some injectors.

Porting the manifold and O2 sensor housing was one of the last things I did to my Spyder. I was pushing over 35lbs/min on an unported manifold and O2 sensor housing.

 

[boost97gst]

The porting is always a good idea. Use a very nice carbide bit, dont want to cheap out or else youll fail immediately(or the bit will ). I ported the exit of my mani(2g) and ported the hell out of the o2 housing. Took the divider out. I have recently seen just over 53lbs min. As the temps drop, so does my knock so im hoping to hit about 56lbs/min on pump with this setup.

I would think at 14psi on a 16, 11.4 or so would be fine. Maybe 11.2 afrs. If you have a fmic you can definitely lean it a little bit due to the colder air charge.

 

[Spoolin92GSX]

Those are some great flow numbers for pump! I'm finally getting bigger injectors this week, and I found a friend with carbide bits so I'm digging into the port work as we speak. Once I get things dialed back in with the added fuel and no exhaust leaks I'll get the AFR's back in the 11.2 range. Also, I think I was having a derp moment when I felt the hesitation, or the car was having a derp moment, after I fixed my base fuel pressure it hit as rich as 10.8 and pulled fine