racing with restrictors
Thread Starter
On The Tree
Joined: Apr 2006
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racing with restrictors I'm going to be racing in local class Sand Rally that you have to put a 2" restrictor before the throttle body.
A friend of mine said you could put a vortex device after the intake that will twist the Air into swirl going in.
so my question is what could you do to get the most Air in even with restrictor?
what are your thoughts guys?
A friend of mine said you could put a vortex device after the intake that will twist the Air into swirl going in.
so my question is what could you do to get the most Air in even with restrictor?
what are your thoughts guys?
Teching In
Joined: May 2004
Posts: 20
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I know in NASCAR we made the plenum under the restrictor as bid as we possibly could. Now thats working in a given RPM range and i dont know much about Rally. My comment probabliy wouldnt even apply to what you are donig. I know when a restrictor is involved the limits of combinations and theorys are endless. What does the resrictor look like. Is it a flat machined piece of metal with a given hole size or a nice radius with a given hole size.
Teching In
Joined: May 2004
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Unless someone with experience with these setup chimes in. This will be a tough question to answer. Once a restrictor plate is involved in my experience almost everything you would normally do goes right out the window. I have seen my fair share of restrictor plate manifolds and the only thing they had in common was huge plenums AFTER the restrictor plate. I mean right after the restrictor plate. but that was carb stuff so it might not even apply. The restrictor plate will make even the smallest changes a big deal to a given point. I reground a set of heads for 2 weeks changing the SSR floor angle opposite to the cant of the valve to see if i my theory would hold up. I saw only a 3ftlb increas and 1 maybe 2 hp increase. It did manage to knock the total timing down 4 degrees totla timing but still all that work for 1 maybe 2. Call a good cam company and they should have a good amount of info to share maybe.
Registered User
Joined: Nov 2011
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One way to over come restrictors is to raise your static compression this is a topic of discussion on theoldone.com web site haven't tried it personally but larry the has had his hands in many things over many years might be worth reading
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On The Tree
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TECH Apprentice
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If the rules don't specify a plate, you will want to run a cone with an angle of 13* or less as the tube gets smaller towards the restriction, then taper it out towards the throttle body (the diverging taper isn't as critical) where the two tapers meet at the smallest point, should be a gentile radius.
Easiest way to make one is to turn a large candle on a lathe then wrap it in glass and resin (go slow adding layers so the resin doesn't heat up and melt the wax) when its cured you can melt the wax out in a pan of water. This will leave you a super smooth finish.
Easiest way to make one is to turn a large candle on a lathe then wrap it in glass and resin (go slow adding layers so the resin doesn't heat up and melt the wax) when its cured you can melt the wax out in a pan of water. This will leave you a super smooth finish.
Thread Starter
On The Tree
Joined: Apr 2006
Posts: 118
Likes: 0
Thread Starter
On The Tree
Joined: Apr 2006
Posts: 118
Likes: 0
Unless someone with experience with these setup chimes in. This will be a tough question to answer. Once a restrictor plate is involved in my experience almost everything you would normally do goes right out the window. I have seen my fair share of restrictor plate manifolds and the only thing they had in common was huge plenums AFTER the restrictor plate. I mean right after the restrictor plate. but that was carb stuff so it might not even apply. The restrictor plate will make even the smallest changes a big deal to a given point. I reground a set of heads for 2 weeks changing the SSR floor angle opposite to the cant of the valve to see if i my theory would hold up. I saw only a 3ftlb increas and 1 maybe 2 hp increase. It did manage to knock the total timing down 4 degrees totla timing but still all that work for 1 maybe 2. Call a good cam company and they should have a good amount of info to share maybe.
keep them coming guys
Our FSAE car had a restrictor plate on it that was more like an hourglass shape necking down to the required diameter. We then had a huge plenum 10x the engine displacement just after it before the ITBs. I dont recall the exact dims of the restrictor, but it had several inlet angles and was designed on a flow bench. Ive seen a few ASA LS1 restrictors and they're just a disk of aluminum with a hole cut in the middle
Teching In
Joined: May 2004
Posts: 20
Likes: 1
Is there a picture of what the restrictor plate setup looks like? if you are able to put something before and after the restrictor, then playing with radius inlets will make HUGE gains. Pretty much turning the restrictor into a venturi. I wish i had my old pics of our manifolds to show you some things we tried.
