BATMAN

From my personal experience and that of others in the RX7 and piston arena Jethot does indeed reduce underhood temps that u can actually notice when u open the hood and place ur hand over the area that was treated. the temperture drops are significant to be noticed.

Generally, the rule of thumb is that the greater the heat in the air the less molecules, such as O2 is present in a given volume of air. Air expands and part of that equates to less O2 per given volume. SO with that in mind ideally u want to get more O2 in via colder temps.

The analogy can been experienced when u breath in a cool night. It's easier to consume greater O2 (from what ur body's mass air sensors can tell u) with each respective inhalation.

If u were in the same elevation where the air is hotter, u will have to inhale greater quantities of air to get x amount of O2.

There is also an ideal operating temp (which I have heard is 160 degrees) that allows the A/F ratio to expand at the millisecond prior to the combustion event. I am not sure if this is just theory or absulote fact since my expertise is rather limited in this area.

Tim, please confirm and amend.

BLUE TII

iTrader: (9)

Aw, you FD guys have such cute little primary runners

I did not extrude hone, but rather made a 10" split mandrel for a die grinder and immersed the lower end of the manifolds in water and hogged out the runners w/ 80 grit emery and polished them up to w/ finer and finer emery them wet/dry cloth backed sand paper.

I was able to reach all of my '89 LIM and my '93 UIM w/ this method. I was able to get the '93 primary runners hogged out to match the '89 LIM- it goes pretty fast when you get the right mix of water, emery grit and rigidity and die grinder speed.

I roughed the LIM 2ndary ports below the 2ndary injectors w/ 80 grit perpendicular striations. I believe this will create a thicker boundry layer and help prevent fuel from the 1600cc 2ndaries from condensing on the floor of the 90 deg. bend right below these injectors.

I had to REALLY up the fuel VS coolant temp maps on the Haltech as fuel really did whet on the intake manifold horribly on cold starts. It is like steam vapor on a cold bathroom mirror. The reversion charges from the large streetport overlap push the primay injector air fuel mix back up the runners and it condenses on the polished surface.

I have the intake apart now after 9,000 miles and the primary runners have a golden sheen from varnish of cooked on fuel. The 2ndaries (Bosch 1600s) just where I roughed them are black. Everything is pretty much polished up the way I did it- very impressed!

All the work I did to my intake should have killed the low end flow. Removed the 2ndary 2nd throttle blades and bridge, made 2ndary plates move right w/ primary plates, ported/polished everything, really hogged out the primay runners.

But, the low end power is great for me. I think low end really depends more on how big your exhaust is and a properly sized turbo. I am into boost by 2,000rpm.

Now that I have it apart I am really thinking of the Jet Hot coat. Sounds like a killer idea.

Flybye

Since Glassboy did the honor of posting pics of the Extruding, I guess I'll post pics of my Jet Hoted intake....assuming Rallimike used the same coating

the_glass_man

iTrader: (2)

Looks nice. I've been thinking of doing my IC piping as well. Less work then having to keep them polished.

Tim Benton

iTrader: (1)

do the inner ic pipes with the 1300 ceramic based paint you can get at the autoparts store. Since the intake charge temp never gets that hot, it should be enough to help the piping not get to hot.

Tim

BATMAN

The UIM would have looked better if it was polished and then Jethot coated near chrome.

tekno62

I have to agree with Batman on it

BLUE TII

iTrader: (9)

If all the $$$ for Extrude Hone scares you, here are pics of what you can do yourself w/ a die grinder.

















Why stop at the intake manifolds? I did my entire intake and exhaust tracts.

Here is a pic of my reworked Isuzu NPR IC- originally it had big casting bosses inside the endtanks



It is all coated w/ the VHT bake on 1200 deg F paint.

rallimike

iTrader: (1)

My car goes to KD to have the manifolds installed, along with some other stuff in a couple weeks. Beyond having the manifolds coated, I also had a 3/8" phenolic spacer made to go between them, and, obviously, the studs aren't long enough to accomodate the spacer. McMaster-Carr doesn't seem to have any studs close to what I would need. Is there any reason I couldn't use bolts to fasten them together? Does anyone have any other suggestions?

BLUE TII

iTrader: (9)

Bolts down into the LIM to hold phenolic spacer and UIM to LIM?

I would not use bolts into any aluminum if I could help it. I believe the reason all factory connections into aluminum use studs is the bi-metalic corrosion is likely to sieze the two materials together.

If you really can't find studs long enough, you can buy high grade bolts longer than you need and cut the hex heads off and champher the edge.