Hank's HMMWV, we're going to war! (or at least the shops)
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Hi Yes we're a bit optimistic we might get something out of sealing up the two pipes of the external wastegate and reactivating the stock one. I believe the orginal stock wastegate was tack welded shut. It doesn't budge and visually looks closed and sealed. The car has noticeably more lag so it could be at least part of the problem, maybe all. It's definately one of the key changes made since last tune. And it's one that's more difficult to fully understand and measure, not like for instance timing or cylinder compression. Thanks for that feedback, we'll let you know how this progresses. Fingers crossed. Regards Rob -
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Well, I was going to say, "Is the wastegate set up so that it is not leaking?" That's actually a different thing to what you're asking about. In theory, if you have allowed the two halves of the manifold to commmunicate (more than the stock manifold does - which is at least a little bit) then the negative effect should be apparent in delayed spool, not in outrigth power. OK, maybe just maybe, a badly set up twin scroll wastegate "crosstalk" might kill the top end, although it's hard to see how. What is happening with the original wastegate in the turbo? is it sealed off properly. If it's left flapping in the breeze, it will f**k everything up. If it is still there, and can be returned to service, I'd be capping off the external (presuming the two halves can and will be isolated from each other after doing so) and have a go with just the stock wastegate. I have an internal wastegate in my highflowed rear housing. The bigger opening and flapper should be fine to >250 rwkW. So there's not exactly a pressing reason to have the external. Done right, an external will give better results. Done wrong, it might just be possible to have worse results. Report back!
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Hi Rob It's a nistune ecu. Yes same shop, good reputation. Apparently the computer on the dyno is compensated for temperature. Chris was saying that the lean or richness of the mixture would be covered in the actual tune, but he's already picking up in advance that it's under what it should be. Regards the dyno, it's also noticeable on the road. But I just want to add something that has just come in, it appears there might be something in the setup of the external wastegate. In the exhaust manifold there is a centre divider between the front three and rear three cylinders. The external wastegate has a pipe from each side that join at the wastegate. Theory is those two pipes just might be pypassing that divider and introducing a problem somehow. Is anyone familiar with the divider in the exhaust manifold and the effects if the two wastegate pipes were to create a bypass path? Thanks for your questions Rob, interested in your thoughts on this external wastegate bypass theory. Regards Rob
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