Ok, need some advice.

Here is my build -
11.5 JE Piston, the latest one out.
HR2 cams.
Ported Head, got it from Pipelayer.
TM45 carb.
Big Gun CDI
One of my F4i slipons.
No-Toil, snorkel, no airbox.
Wideband O2 sensor for tuning.

Today I started tuning with the O2, and found I was rich on the main circuit. The rest of my settings were ok.

From what I can find reading on O2 tuning I should be looking for around 12.5 to 1. I was around 9.9 to 10.5 A/F ratio at full throttle in 4th gear on a long uphill pull on asphalt. If I lean it even a little bit from there I start to ping.

I can only get 91 Octane pump gas, is this just not enough with the mild cams and the 11.5 piston?

Is the 9.9 to 10.5 an ok number for the DS?

Its around 90 here today with very little humidity.

Thanks in advance,
Scott

 

on the dyno I tuned for max power while ignoring the a/f readings until I achieved max power, then looked at the a/f to see where it ended up, and it was between 12.5 and 13:1.
if you are pinging to the point of being able to hear it, I would think the octane is too low, imo. I ran 93 octane with my old school first generation je 11.5:1 for many years, sometimes ran 92 also if I wasn't around any 93 to be found, but never experienced any pinging. but that was the old school piston though, that from what I here may not have quite been 11.5:1 and is said to actually be closer to 11.2:1.

 

Thanks Hightower,
Last year when I got dyno'd my DS before my build the operator told me that the best pwere was between 12 and 13 to 1 and that did dyno out the best for it at that stage.

I think you are right about my gas, I'm going to get some race gas and mix it to see how I do. I do not want to run it with any pinging.

I will then get it up to the 12.5 range and see how it does. I just was hoping to get by without using any race gas.
Scott

 

This is what stinks. . . the O2 sensor will foul with race gas (leaded fuel).

If you run a mix of fuel, I would suggest you tune it then take out the sensor and plug the bung.

From what I've heard Hightower is right on with the A/F ratio. . . about 13:1.

The nice part about the closed-loop FI systems is the O2 sensor will make adjustments, the downside is the sensor will fail with leaded fuel (race-gas).

Did anyone see the article in Qu4d about Fuel Injection Systems last month? Great article. That magazine is doing a great job on their articles.

 

My plan is to tune it and take it out. Hope ot only have like 15 to 30 min to dial in the main.

I'm going to pick up some race fuel tomorrow. The local shop had VP or Trick, they say they are both 110 octane. Trying to decide if I should try a 1/3 or 1/2 ratio of race gas to start with.

I did see the Quad article. I like that mag also, been a suscriber since the first issue.

 

A 1/3 mix of race fuel will probably be enough

 

I would agree that mix should do it for you, but I would go 50/50 to be safe. VP makes some good fuel also.

The other thing I would remind you, is that you keep in mind the temp and humidity that you are dialing in with. If temps drop a lot in the next couple of months and humidity does not go up, or you travle......You get the point.

 

Maybe I'm missing something here but 11.5 to 1 should work with pump gas. Unless you have the ign timing bumped to the moon a "true" 11.5 to 1 should work. Are you sure it's detonation your hearing? Does the plug show signs of detonation?
If your on a budget you can throw about 5 to 10% toluene in the tank. Same with methanol. With the methanol you will pick up a bit of power.

 

Doctor Turbo, from all I have seen and the builders I have talked you are right about the 11.5 to running on pump gas, that is why I chose to run it.

Also, I have heard rumors that the older JE11.5 to was ran a little short of a true 11.5 to 1 (Hightower and other places) and that the newest JE are running a little higher than a true 11.5 to 1.

I do not know my true timing, just that I'm using a Big Gun CDI.

It is pining, but I only have heard it when I started leaning it past where it is now, 9.9 to 10.5 to 1 A/F.

I know you live here in Lake County, is there someplace open today that has Toluene? I was just going to go to Hillside Honda and get Some Trick 110 for testing, but sure don't mind trying the Toluene if its cost effective since its around 114 octane.

 

Tri-valley is open to noon I think. Piedmont will have some too. It's a cheap way to go and works great. I used to do with my turbo cars. Try 5% and see if it cures the ping. 5% should be more than enough for your deal.
It's very strange you have detonation. A lot of things can cause it though. Cam timing, fuel to air, ign timing, yada, yada, yada.