scathcart

Well, I snapped a couple pics after roughing in some mild race ports. A while back I was asked to post some exhaust port pics... so here you go.

Timing is:
Exhaust Open: 80* BBDC
Exhaust Close: 70* ATDC

Stock:
Exhaust Open: 72* BBDC
Exhaust Close: 48* ATDC

These ports have been roughed in ONLY. Finish shown is done with a 120 grit drum... I end up going back with a 220 grit drum, to finish the bevel, and then hand polishing with wet sand paper up to 2000 grit, followed by polishing. I'll grab some pics of the final product later; the final finish is almost chrome.

These will be used on a high-comp bridge ported engine. Idle 1500-2000, usable power above 6000 rpm. Should be fun. No header on the market will currently fit. I have to build one to fit. The design will help to fill out the shape of the exhaust port.



Here is the degree wheel, mounted, with the pointer attached to the front cover. This is how a person knows their EXACT port timing, and is able to accurately mark the front pulley.


Here's a shot of the rotor sitting on the iron, showing what the exhaust flows out.

scathcart

Sitting beside a stock port:




And here's a shot looking at a used apex seal through the exhaust port. You can see here how I'm going to have to work the header; the pipes will actually stick into the rotor housing.

geargrabber

cool dude!

scathcart

From here I press in some aluminum plugs to block of the air injection holes (two external the engine, and then the one pictured in the port), and then clean everything up.

88IntegraLS

Hm, interesting, you went up more than down from the stock port.

scathcart

Big overlap.
I don't like to go down all that much. I find it cuts into the power stroke.

GtoRx7

iTrader: (5)

Those are very nice ports you did!! I did a "race port" from racing beat template, but I dont think it was quite that high, maybe it was...? Is this going to be for a street port intake, or bridge? Nice work again!

scathcart

RB race ports close 13 degrees earlier, and open 8 degrees earlier than mine. So yours would have gone down quite a bit more, and not gone as high, you're correct.

EO: 88* BBDC
EC: 57* ATDC

This is for a bridgeport.

trochoid

iTrader: (6)

Does all of the extra polishing pay off that much? I understand the reasons for not polishing the intakes that finely, but I'm not sure if it is that necessary on the exhaust either.

Some areodynamicists have discovered that super smooth surfaces can actually increase the boundry layer friction. A textured surface, such as the bumps on dolphin skin, or the scales on a fish, actually reduce the boundry layer friction of the laminar flow. I realise we are dealing with gas flow and not liquid here, but the only difference between the two, behavior wise, is that gas is compressable.

Any thoughts or comments? Beautiful work, btw.

scathcart

You sound like a fellow engineer.... cheers.

I don't polish for improvements in exhaust flow. The flowbench says there is next to no difference between the shown surface texture and a perfectly polished one. I do it to keep as much heat in the exhaust charge as possible and to reduce the chances of carbon building up on the port walls. Rough carbon deposits DO hurt flow.

trochoid

iTrader: (6)

Unfortunately it is kinda of a lame B.S. in Construction Eng.. I did have some fluid dynamics though. I heartily agree with preventing the carbon build up and the heat transfer should be less due to the reduction of surface area.

It would be nice if that small exhaust area with in the housing could be ceramic coated. Less polishing and heat transfer.

scathcart

It can
Just not on this engine.

GtoRx7

iTrader: (5)

I have not done a search under your name, so hopefully this is a good question. What car are these housing going into? N/a or turbo, ect ect. I am just curious about your project.

Sideways7

iTrader: (7)

He said its a high-comp bridge port, so I'm guessing its a non-turbo.

felixwankel88

o man, thats gonna be a geat engine

scathcart

Its not my car, but its going into a canadian base mdoel S5.
No sunroof or any accessories.
When I started, the car weighed 2510 lbs with a full tanks of gas, no driver.
When I am done, it will weigh ~2340 lbs with a full tanks of gas.
I am also throwing on the brakes, the LSD, doing the tranny, the clutch, etc etc.

The engine will be run N/A. Eventually I think the owner plans on throwing on a very large turbo and seeing what kind of power can be put down... with the high comp rotors, I am methanol will be the most suitable choice of fuelling when this situation arises.

The owner does intend on driving it on the street.

scathcart

Yeah, I am documenting the entire build-up... I've got pics of a lot of stuff, I'll throw them up when the car is done. This is just a bit of a teaser.

I've got pics of designing ports based on the port timing, how to locate TDC with a degree wheel, how to choose and clearance your bearings, how to re-work the oiling system for better cooling, higher pressure, and better flow, welding up your solid engine mounts, oil pan, header, modifying the oil pump and gallery, polishing rotors, etc etc etc.

run_rabbit_run

More pictures! :P

The owner of this buildup sure is lucky to have a friend like you. I bet it's going to be _killer_.

rotarygod

iTrader: (1)

Revival of the year old thread!

Sideways7

iTrader: (7)

Yep, pretty much. I was reading through, and saw my post. It confused me because I didn't remember this thread, then I saw it was a year old.

run_rabbit_run

Heh. I know of the car he is talking about, I just didn't realize he had created this thread about it (I stumbled across it while creaping about online)...reviving the thread was a bit of an inside joke.

Kyrasis6

Got links? I'm very fluent with how to do all of this stuff on a piston engine but on a rotary could only make an educated guess and hope it is right.

Thanks,
K6

My5ABaby

iTrader: (7)

Crazy bastard.