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Split Pulse Manifold & Wastegates
Here is a post that I saw on another forum and it makes sense to me. I don't think I have ever seen a split pulse manifold with flanges for 2 wastegates.. What are people's thoughts on this?
Theres alot of Umm's and R's when it comes to Turbo's. With a few years of racing Turbo cars and modifying them, we have tried every trick in the book. One thing I would like to discuss is Waste Gate set-up. * Have you ever wondered how much difference it makes to set a turbo up for split pulse? Well if you are using a single Waste Gate you won't gain a damn thing!!!!! You think about it, 1 pipe from each extractor, eg. a Mazda Rotary, 2 pipes one for each rotor, 2 separate pipes heading to the Waste Gate, sounds all like high tech stuff, and that each port of the turbo is getting a separate pulse!!! (WRONG) were the pipes met for the Waste Gate they come into one letting a pulse from one side sneak to the other before the valve. This is transforming the system back to a single pulse set-up. To make the set-up to work correctly two Waste Gates are needed one for each pipe. You think about it when it comes to 4's, 6's & 8's. Just something for you to think about!!!!!!!!!!! |
The manifold i am going to get made has two seperate wastegates, one per runner, its totally split :)
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So does that mean that you agree with the theory that you are not benefiting from the split manifold if you have a single external wastegate? I have seen pictures of the RICE RACING & Crispeed manifold and they only have a single wastegate setup. Those guys wouldn't make something that had such a potential flaw in the design so I think that something must be missing from the equation.
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If you look at gregs manifold (one of crisspeeds) it has two long tubes running to the wastegate only connecting at the end. I can see how this would bleed some of the pulses to the other side but my guess is that it woulden't be all that much.
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As long as the wastegate pipes each had 2 "s" curves in it, the chances of the pulses wiping each other out are slim, dual wastgate would be ideal, it would make the piping alot easier, however with the cost of wastegates, its not economically feasible, pipe is cheaper than wastegates. The reasoning mainly for the divided is also to keep velocity up in the gases, instead of dumping into a big open chamber, considering the wastegate is closed when the turbo starts to spool, I can't see much flow going through wastegate piping..Max
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I can see it posing a problem. The difference in the real world though? :-)
Anyone with some spare time can run the numbers and see what sort of main pipe/connector pipe lengths and volumes we'd shoot for to minimize this. I'm guessing that once the thing is good and spooled, the pulse equalizing flow through the connector pipe would actually help things. |
according to a rotary guru on this forum, with stock ports or extended ports you should aim for 13inch runners between the exhuast ports and the turbo. 11inches on a PP
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