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art leong

Map signal?

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I'm running Individual throttle bodies. I have a vaccum box about 1 inch sguare x 6 inches all four intake runners feed it.

My problem is at low rpms with vaccum the signal bounces like mad. At wide open throttle it is fine but driving around the pits it is eratic and hard to tune. I'm thinking about using a restrictor in the line near the ECU this might calm the signal down, or maybe a pair of restrictors leading into and out of a mini manifold.

Does anyone have any thoughts on this?

Thanks

PS this is a naturally aspirated motor, no boost.

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Maybe you can use dual map`s and run on tps below a certain map set-point?

I had to use tps instead of map at low loads and idle on my bmw m10 turbo with 304* cam due to high "overlap"and lack of vacuum.

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As far as I´m concerned, N/A engines are always tuned TPS as primary load source. With Vipec TPS as primary load source for boosted engines works like charm also.

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You can also build a small canister, 3 in long and a 2 in pipe with caps welded on the ends. Then put the vac line feeding into this and one coming out and it will mellow out the large pusle. It works well with my large bore 2 cyls and ind throttle bodys..

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If you have cams with large overlap, you will get a very weak manifold vacum and it is useless to try to tune with map as load. Use tps as load.

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I have 3 races in 3 weeks coming up. As soon as I get them done I'm going to change to TPS instead of Map. Don't want to change it before the races. It's running fast enough now to get me in trouble. I play when there are no NHRA eyes around.

Thanks all,

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You can also build a small canister, 3 in long and a 2 in pipe with caps welded on the ends. Then put the vac line feeding into this and one coming out and it will mellow out the large pusle. It works well with my large bore 2 cyls and ind throttle bodys..

That is what I'm going to do right now, with a vacuum restrictor on the map side. It should make the car run cleaner in the pits. Cleaning fuel fouled plugs before I stage is part of the problem

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You can also build a small canister, 3 in long and a 2 in pipe with caps welded on the ends. Then put the vac line feeding into this and one coming out and it will mellow out the large pusle. It works well with my large bore 2 cyls and ind throttle bodys..

Did this used PVC pipe and put a vacuum restrictor on the MAP side. I helped a lot. Now it varies only 5 KPA at most.

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