[CraigG.]

Hey Guys,

Prepping Northwind with a Dominator for E85 and wondered if a rough runner and plenum finish is ideal for heat transfer and air fuel mixing?

Thanks Again, Craig

[455firebird1969]

Hey Craig,

I’m far from being an expert on this topic, but everything I have read on porting heads says the intake surface can and should be left rough, no polishing necessary.

I had a set of Hi Port heads & Northwind intake ported by Dave Wilcox a couple years ago, and I am finally getting around to building the engine I envisioned with these heads & intake.

I’ll post a couple pictures of the intake so you can see Dave’s work, and the surface finished he left in the plenum and runners.

As far as heat transfer and the intake charge goes, I’m not so sure the surface finish affects it much, but like I said, I’m no expert.

Everything I’ve learned about running E-85 is to treat it like gasoline. Yes, the Ethanal has an additional cooling effect on the engine, when compared to gasoline, but I believe that is the biggest difference from gasoline.

I’m sure you know you must put more fuel into the tune, and the requirement to get the engine up to 180 before staging the car, so it doesn’t stumble on launch. Once you have accomplished these two requirements, it pretty much runs like gasoline from my experience.

[CraigG.]

Thanks Axle -

Is that your T-2 and curious about the flow?

Is there any advantage to bur finish over the smooth (manufactured) finish for the plenum floor?

Thanks, Craig

[krisr]

As ^^, i've always just treated it like gasoline. If you're new to the E85 game though, definitely pay close attention to the maintenance schedule and change the oil more frequently. I found in my street car I was changing the oil every 2500kms and when it came out, it was a very watery consistency. Figured it's just the way it is.

[CraigG.]

Hey Guys,
Thanks for all your thoughtful input as I always appreciate learning.
Hopefully we'll all get to the track this year.
Craig

[Tom Vaught]

If the finish is smooth you will have fuel puddling in the intake off the plenum walls and the fuel will run where ever it wants causing random fuel distribution issues at all rpm points. Dave Wilcox is a smart dude.

Tom V.

[CraigG.]

Tom does that include the plenum floor?
Thanks, Craig

[455firebird1969]

Craig

That’s my NW that Dave ported.

I’ll post a picture of my T-II. If I remember correctly it’s still pretty much untouched in the plenum and runners. I bought it used with the heat crossover already removed, so the previous owner did a little work to it, but I don’t think I did any more.

[Tom Vaught]

Originally Posted by CraigG.

Tom does that include the plenum floor?
Thanks, Craig

Absolutely, the fuel comes off the walls in droplet streams (like rivers) and migrates to whichever cylinder can exert force on that stream of fuel.

The fuel then enters that runner and you get a rich spike on a random cylinder event for that cylinder.

I "KNOW" (vs assume) because we put cameras inside the plenum to observe the air/fuel patterns during the idle phase, the "Tip-In" phase, etc.

Cubic money for the equipment but knowledge costs money.

And it is random when it gets drawn into a given intake runner, but based on the intake design, some cylinders get more liquid fuel "rivers" vs other cylinders due to the engine installation angles.

Now if the heat riser and cross-over passage is working properly then you have the fuel remain a vapor above the cross-over passage and inside the intake plenum.

Common sense, when you think about stuff, goes a long way in figuring out issues. BUT sometimes having the right equipment (like the very expensive intake plenum cameras) locks in your theories or blows them out of the water, lol much quicker.

Tom V.