(Not*) Mediocre 242

[bobxyz]

My guesses from the other thread was:
- there was huge overfueling at idle (~5x more than a normal redblock at idle)
- the overfueling with the big cam overlap results in the mixture still burning/expanding when the intake valve opens
- which allows exhaust gases to be pushed into the intake manifold, killing the vacuum

Can you look at the logs and see what the idle fuel flow (in cc/min) is around idle? Or, if Motec doesn't log it directly, the injector pulse width, deadtime, and flow rate around idle.

 

[t8fanning]

so, interesting my RSI head with the stage 3 cam pulled more than 8in at idle, I'd have to go back in time and look for values but I know it dropped with the big Kyrk cam. And now with the same Kyrk cam as you I'm at 8in at idle (watched it on tuesday with your car in mind). I know we both timed the cam to Reine's specs... still don't understand the difference there. My pedal definitely gets stiff around idle but it hasn't been enough of a problem to go after a solution.

I might have some vacuum leak somewhere in my manifold or something, but I've never had really good idle vacuum. It also might be because I have a torque converter and idle right around 1000 rpm instead of a clutch.

 

[t8fanning]

My guesses from the other thread was:
- there was huge overfueling at idle (~5x more than a normal redblock at idle)
- the overfueling with the big cam overlap results in the mixture still burning/expanding when the intake valve opens
- which allows exhaust gases to be pushed into the intake manifold, killing the vacuum

Can you look at the logs and see what the idle fuel flow (in cc/min) is around idle? Or, if Motec doesn't log it directly, the injector pulse width, deadtime, and flow rate around idle.

I'm at like 60 cc/min at idle on this new head. On the old head with RSI stage 3 cam it was slightly more than that ~63 cc/min or so.

 

[andyb5]

I might have some vacuum leak somewhere in my manifold or something, but I've never had really good idle vacuum. It also might be because I have a torque converter and idle right around 1000 rpm instead of a clutch.

Altitude might be part of the difference between the different measurements on your two cars?

 

[t8fanning]

Altitude might be part of the difference between the different measurements on your two cars?

Could be, but I'm pretty much at sea level and I think Mike is pretty close to that.

 

[bobxyz]

I'm at like 60 cc/min at idle on this new head. On the old head with RSI stage 3 cam it was slightly more than that ~63 cc/min or so.

I'm even more confused with this. My B21FT LH2.4 and a basic B230FT MegaSquirt both idle around 7 or 8 cc/min. My wagon cruises at 65 MPH at ~35 cc/min. What am I missing, or where's all your fuel going at idle?

 

[t8fanning]

I'm even more confused with this. My B21FT LH2.4 and a basic B230FT MegaSquirt both idle around 7 or 8 cc/min. My wagon cruises at 65 MPH at ~35 cc/min. What am I missing, or where's all your fuel going at idle?

Maybe one of our fuel models isn't accurate. I don't know.

 

[culberro]

Maybe one of our fuel models isn't accurate. I don't know.

The embedded motec fuel model is insanely accurate when paired with a fully characterized injector like what Injector Dynamics offers.
Like it’s within 100cc of fuel used after racing for 40min.

I'm even more confused with this. My B21FT LH2.4 and a basic B230FT MegaSquirt both idle around 7 or 8 cc/min. My wagon cruises at 65 MPH at ~35 cc/min. What am I missing, or where's all your fuel going at idle?

Into the exhaust.
Big cams are the anti efficiency at low engine speeds.

 

[t8fanning]

The embedded motec fuel model is insanely accurate when paired with a fully characterized injector like what Injector Dynamics offers.
Like it’s within 100cc of fuel used after racing for 40min.

Luckily I get to use their built in fully characterized model for my injectors. My only gripe is that Motec once predicted I was using 70 lb/min of air, which is an overprediction based on my dyno data. I'll have to try and hunt that inaccuracy down at some point.

 

[culberro]

Luckily I get to use their built in fully characterized model for my injectors. My only gripe is that Motec once predicted I was using 70 lb/min of air, which is an overprediction based on my dyno data. I'll have to try and hunt that inaccuracy down at some point.

That’s interesting about the air flow difference. It’s been a decade since I’ve used any Motec product. They didn’t even have that feature unless you made your own math channels.

 

[t8fanning]

That’s interesting about the air flow difference. It’s been a decade since I’ve used any Motec product. They didn’t even have that feature unless you made your own math channels.

I'm sure I just have some setting wrong somewhere throwing it off. Just haven't tracked it down since there's always a bigger fish to fry.

 

[t8fanning]

The new coolant expansion tank showed up.

And promptly did this on the first drive.

I had no idea they were two pieces. My hose must be a bit too short and is pulling on the tank. I'll have to epoxy it together and run it. It still leaked though independent of the bracket split, so I'm definitely gonna pull the head when my gasket shows up.