205/50 on 15x8's or 225/45 on 15x9's, depending on the event. Nothing unusual.

 

Curious why you have it running richer in the mid vs the top? I used to tune the higher RPMs 13.0 or slightly richer to help keep it cool, maybe I was doing it wrong? Anything below ~75 kpa I tuned it to 14.9 for more economy.

 

Because thats how N/A engines are tuned with it's VE peak somewhere in the midrange. You ran 14.9 at full load? That's deep into piston melting territory even N/A. We run a bit richer than 13.0 near the VE peak and close to 13.0 where it runs out of cam on top. Just back from full load, around 80kpa, we abruptly dial it back to 14.7 then leaner at very light load. Most of the fuel savings comes from carefully dialing in transient and closed throttle. We want as much torque as possible so we're not starving it for fuel where it wants it.

 

Thanks for clearing that up.

The 13.0 v 12.8 sounds about right, it sounds like it has a healthy "area under the curve." I simply always thought 13.2 was prime for N/A, so I always followed that, and tuned it richer in the higher RPM to keep it cool, even if it was losing power.

I tune 14.9 anything UNDER ~75 kpa (not sure where is best to transition, 70kpa or 80kpa)-- not at full throttle. I know the engine would be toast by now if I did lol.

 

Every motor is a bit different. Some might make peak power above or below 13.0. The rental motor we did two years ago made best power at 13.2 like you have observed. Much leaner than that on a stock long block is getting risky. For this tune, we played with AFR, spark, injection timing, VVT, exhaust cam timing to see where it made the most torque everywhere up to our 148whp limit.

A big part of this tune is track testing every tweak we do. Might look awesome on the dyno but drive like poo. We still have one or two more visits to our neighbors dyno so I can tune the map how I really want it.

 

Intentionally reducing engine VE by retarding the intake cam at all RPMs below 80 kPa can improve BSFC aka fuel economy because it reduces pumping losses.

 

Exactly. That's one of the reasons we chose to use a VVT engine.

 

Did you consider retarding the intake cam gear a tooth retarded from stock?

FWIW my car likes full retard by around 5800 RPM IIRC. At WOT / mid RPM it doesn't like even halfway to full advance. So if I jumped it a tooth I could get even more retard, and still have margin for full advance.

Perhaps the extra retard would further improve part-throttle BSFC.

 

Looking forward to the race. I'll be driving either a 2012 Grand AM Spec Civic Si or a RSX-S that was built for enduros. I'm not sure if our cars are E0 or E1, but either way we won't be racing you guys. So good luck in E2 and see you guys in a few weeks.

 

I had some advance headroom after I found peak torque below 5000 rpm. I bet there's enough to account for the extra tooth. I think I ended up at at about 36 or so crank degrees of advance from full retard to get max torque. that leaves another 10 or 15ish of additional advance. One tooth off is 15.6 degrees...

 

You two are both turbo right? I'm using all of the advance in one part of the map. Not sure how much I would benefit as it is already detuned on top. Andrew Kidd of TSE will be our head mechanic for T25. He also suggested the skip tooth.

 

Happy to hear the miss is all squared away. Best of luck. What a machine.

 

Yes I have a turbo, I don't know if y8s still does. (Wuss!) AFAIK he did his VVT tuning *with* the turbo.

All of the advance? That's pretty surprising.
Although a turbo motor would tend to want less advance.

Certain you didn't time the intake gear wrong?
Or set up the ECU wrong to that either
- you think you're at full advance but you're not
- you clipped the max advance in the setup, far from the VVT's actual max advance

 

Jason,

ECU and timing belt are correct. We are where we want to be. All of the advanced tuning ideas have been implemented. We're just fine tuning now.

 

of course i still have a turbo!

and I dont know that it affects how the vvt works all that much. it may change things a bit due to changes in charge density, but it's still very much tied to RPM and not so much to manifold pressure.

I need to do some more testing and tuning now that I have a better way to control it with the MS3.

Emilio, you're running all 48ish crank degrees of advance? Is it before 4500?

 

Y8s,

Shoot me an email for more info on the tune.

 

With my GT2560 I find that it wants less advance (less overlap) in the midrange, at 15 psi, than at 10 psi.

It stands to reason that as the limits of a turbo are reached, backpressure increases faster than manifold pressure, and thus it wants less overlap.

 

I see a re-route in use - you are using the BP26-10-271 head gasket? Did you open any additional passages through the gasket or leave it as is?

 

It's not charge density that wants to change VVT phase, it's the relative exhaust port backpressure (aka TIP, turbine inlet pressure) vs. manifold pressure.

 

ie the charge flow slows when TIP gets higher relative to MAP?