Target AFR

[jpwalt1987]

Well I am finally getting a chance to do some WOT tuning with the BS3. I am setting up a street tune because race gas is just too expensive and hard to come by. The basic tune is 17-20 psi and 24-21degrees of timing. I made a blast and the AFR held pretty steady at 11.5:1. There were some spots that went a little bit lean and then a little bit rich. I have worked on trimming them into place at 11.5:1. The car feels stupid fast at the boost level and there is NO knock on the knock detector. Should I try to run a richer AFR of say 11.0:1 or what?? I want a safe tune for 93.

 

[jpwalt1987]

Guess i should tell a little bit about the combo.

231 ported GN1s(249/219cfm)
224/224 .560 lift solid roller
PTE front mount
PT-70(old school)
9.3:1 compression
1.65 T&Ds
3800 stall 10 inch ATI convertor TH400
95lb/inj
A1000 pump and -10 line.
GEN1 BS3
single 3 1/2 from turbo to tail pipe

 

[TURBO 6]

Jeremy, IMO 11.5 is a liitle lean. 11.2 is the most I'd go to keep it safe.

 

[QWKRTNU]

11.5 is a little lean. I like to keep mine at 10.8 - 11.0.

 

[HighPSI]

Be careful running at 17-20 psi on pump gas witha a 9.3:1 motor

 

[GNVYUS 1]

You'll make more power at that 11.5:1 straight gas ratio but keep this in mind.

A fatter tune will slightly mask a cylinder on the edge of detonation. Tuned a car from 9.6:1 to mid 11's and it started knocking now really early at the same psi. Though 11:1 might be considered SAFER it's also probably not going to make the power the slightly leaner ratio will. Car mentioned made more power 2k rpm earlier with the knock.

Keep Highpsi's comment in mind and don't get greedy, your tune is very good if you're pushing 20psi with 21 degrees in 3rd with 93.

 

[Boost231]

a few things like posted above. with the compression you have i would be carefull with your current state of tune. i would richen it up some and back the boost down. now if you have endless amounts of money and dont care if the motor lets up just keep and eye out with the way it is. but if it where me i would fatten it up

 

[street6]

17-20 psi, 24/21 timing, 9.3:1 compression, 93 pump gas, and no knock is impressive.

any alky?

 

[jpwalt1987]

I rechecked the compression ratio and I was wrong on the 9.3:1 part.
Gn1's have a 46cc chamber and the Diamond pistons say that should put it around 8.6 -8.8:1. I have the .040 Cometic headgaskets and the heads have some chamber work done on them.

Does anyone think that the cam would be affecting cylinder pressure down in the rpm range helping keep knock at bay? The cam pulled to 6700rpm without falling off. Keep in mind this is a 224/224 solid roller with .560 lift and the springs to match.

I do believe that I will bring the AFR down to the 11.0:1 - 11.2:1 range.

Cal, Are V/E values of over 100 allowed? I am not that high yet but I could see that they could end up real close to that. At 5200rpm and 24psi I have a V/E value of 94. I am keeping the street tune down in the 17-20psi range

Thanks, Jeremy

 

[JayC]

I think 10.8-11.0 is what Id shoot for with that combo. Youre a tad on the lean side.

 

[jpwalt1987]

I think 10.8-11.0 is what Id shoot for with that combo. Youre a tad on the lean side.

Well Jay, you know what they say.... Lean is mean, but a Fat pig lives longer!! I am going to start in the 10.8 range and go from there like you suggested. I need to make some blasts after adjusting the fuel and check the plugs also. I dont want to kill this motor just yet.

The plan is to get the "low boost street 93 only tune" dialed in then make another file for a "93 and Alky tune" with higher boost and probably only another degree or two of timing.

 

[JayC]

Well Jay, you know what they say.... Lean is mean, but a Fat pig lives longer!! I am going to start in the 10.8 range and go from there like you suggested. I need to make some blasts after adjusting the fuel and check the plugs also. I dont want to kill this motor just yet.

The plan is to get the "low boost street 93 only tune" dialed in then make another file for a "93 and Alky tune" with higher boost and probably only another degree or two of timing.

Leaner always makes more power. It just doesnt live as long most of the time. You need to get the tune close and then disable wideband tracking on your BS3 because the alcohol will give you some really rich O2 numbers and the ECM will start pulling fuel. We're using the ISAC to control alcohol via the wideband on Shane's TFS car. I disabled the wideband tracking on the Pro.