C. Ludwig

I've become involved in a project to produce a car for the GRM $2006 Challenge. It will be a Locust Super 7 type car with rotary power. I've been charged with the engine. To make matters simple the person who is in charge of the project has outlined what I have to work with. The engine needs to be normally aspirated. We'll be using injection and a Megasquirt ecu and possibly will have spark control as well. If that's not in the budget we'll rely on a dizzy. The low end of the power limit is 200whp. More is obviously bonus. Total weight of the car should be in the 1200lb range.



I've procured a set of S4 TII 4-port irons and S4 NA rotors. Though I have a couple sets of S5 NA rotors their "fair market value" is a budget breaker. Unless a complete S5 parts car with 4-pot brakes happens to fall in our laps over the next couple months we're stuck with the S4 rotors. We'll be using new carbon seals and new side seals.



My question revolves around the intake. Using 4-port irons we'll obviously need a 4-port intake. I have a couple S4 TII intakes for use. Budget constraints prevent finding something absolutely correct for the j-bridge engine. I have not measured the TII intake yet for runner length but does anyone have any experience in this area and/or advice on making this intake work with the RPM range we'll need to make effective power? We'll have limited machine capabilities due to budget so drastically altering runner length is out of the question.



Any other tips to j-bridge succes?

j9fd3s

https://www.nopistons.com/forums/ind...howtopic=57717



note the use of t2 intakes... note where the power peaks, a bp will be higher. i wonder if some combo of na and t2 intakes would give shorter runners. na plenum and t2 lower with no middle intake?

kahren

why are u doing a j-bridge and not just a street port?

the stock intakes if anything should be lengthened and not shortened for a bridge or jbridge application if you want a powerband under 9k rpm.



on the link j9 has provided, on that manifold i have removed the black spacer between the throttle body and the uim. that was an easy way of shortening the runner 3/8 of an inch its not much but it was easy to do.

heretic

I am picturing two Ford Truck two-plate throttle bodies on a small adapter. The injector bosses are all in the Turbo lower intake manifold so the upper manifold can be relatively easily done away with.

j9fd3s

you could almost make an aluminum box with one tb on the side

C. Ludwig

We want a big bridge just to be rowdy basically. We could get the power we need with an SP but more is better. The technical exercise is interesting as well.



Good ideas on the lower with a plenum. I'll have to break out the math to determine what length of runner we're looking for and go from there.

C. Ludwig

You know I happen to work at KTP. The plant where the Ford Super Dutys are made. I wonder how 5-finger discounts on V10 throttle bodies would be listed in the $2006 budget?

heretic

I don't know, but the common V8 ones are in the neighborhood of 52-55mm and the going price is about $25 each at junkyards, and you get a nice TPS and linear-motor idle air control valve. The IAC is most likely useless, they fail often compared to the stepper motor type, and you probably won't be able to drive it anyway.



You do have to be careful, the throttle bushings like to wear. Not so much a problem on the original application, but it's something you may need to concern yourself with on an individual runner setup.



I am unfamiliar with tbe V10 engine, but the 4.6/5.4 as used in trucks uses a single barrel throttle body very similar to the passenger car models.

inanimate_object

You're pretty much building my dream car, are you building the whole car, chassis and all? What running gear are you using?



I would definitely stick in the lighter rotors, and get the engine revving as high as possible, cars this light don't need much power low down in the range. Are renesis rotors any cheaper than s5 ones? Your best bet by far would be to go ITB's from a big v-twin bike, very cheap off ebay, you have the benefit of pulling cool air from the side, and you're not going to have room for much gubbins on top of the engine anyway.



If you're on a budget I have a few tips if you need them, and I presume locust was a typo, they're made from plywood .



Mark

heretic

It's probably not a typo, and brand new rotors would probably kill the budget. $2006 is the most amount of money permissible to spend on the entire car, including purchasing the car in the first place.



I always loved the car that won the original Challenge, when it was $1500. School bus yellow Spridget thing that they hulled out and put a rare Cosworth Vega engine into. They did a lot of interesting fabrication on that one.