Chris Wilson Posted March 16, 2003 Share Posted March 16, 2003 Did a test this afternoon I had been wanting to do for a while. I had figures for a stock TT setup running 1.1 bar through my decat pipes and an HKS Hyper silenced back end. Today I measured a car with Turbo Technics hybrids on. As many will know, on these hybrids the compressor housing size is increased, but there is no aftermarket turbing housings in bigger sizes available. The backpressure on the stock turbos was bad (18 psi), but with the extra exhaust flow of the hybrids the back pressure was up to 23 psi at the same boost figure. This is an appalling level of back pressure, well over boost level, and knocking hell out of the engine VE (volumetric efficiency). It confirms to me the need for bigger turbos and the acceptance of losing the sequential action, or a big single as the only sensible way to run big HP figures. Just adding inlet air flow with those sort of pressure differentials is a waste of time and money, it just enters a rapid spiral of diminishing returns and excess EGT's . Just thought I'd share this. Quote Link to comment Share on other sites More sharing options...
Nathan Posted March 16, 2003 Share Posted March 16, 2003 Originally posted by Chris Wilson It confirms to me the need for bigger turbos and the acceptance of losing the sequential action, or a big single as the only sensible way to run big HP figures. Just adding inlet air flow with those sort of pressure differentials is a waste of time and money, it just enters a rapid spiral of diminishing returns and excess EGT's . Just thought I'd share this. So, pretty much what I have been saying for years then, and what our data said from the HKS GT ball bearing setup we had on the stock manifold and sequential setup back in 1995. 'The stock sequential setup and turbo configuration is largely useless beyond 450 bhp' Nice to hear it confirmed though Ho hum. Nathan TDI PLC Quote Link to comment Share on other sites More sharing options...
Darren Posted March 16, 2003 Share Posted March 16, 2003 So in 'english' hybrids not worth the money?? Quote Link to comment Share on other sites More sharing options...
GavinL Posted March 16, 2003 Share Posted March 16, 2003 Originally posted by Darren So in 'english' hybrids not worth the money?? That's not what I read Quote Link to comment Share on other sites More sharing options...
Darren Posted March 16, 2003 Share Posted March 16, 2003 That's not what I read Enlighten me then please if you have time? Quote Link to comment Share on other sites More sharing options...
GavinL Posted March 16, 2003 Share Posted March 16, 2003 Originally posted by Darren Enlighten me then please if you have time? 'The stock sequential setup and turbo configuration is largely useless beyond 450 bhp' Hybrids are okay unless you want to go over about 450BHP. Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 16, 2003 Share Posted March 16, 2003 I think this is also the same thing that Terry and Leon found, the stock manifold becoming the limiting factor after a certain point. Chris\Nathan - would i be correct in assuming that if you fitted enlarged exhaust valves (which is a common mod in the US) then this will only make things worse, as the manifold and turbine wheel are struggling to move the increased exhaust gases anyway ? Quote Link to comment Share on other sites More sharing options...
Raoul H Posted March 16, 2003 Share Posted March 16, 2003 Originally posted by GavinL 'The stock sequential setup and turbo configuration is largely useless beyond 450 bhp' Hybrids are okay unless you want to go over about 450BHP. Hmmm, not a waste of money, but not the best solution either. To paraphrase: At 1.1bar the hybrids suffer 23psi back pressure versus stock at 18psi. I'm probably wrong, but I wouldn't have thought that running 1.1bar in either config would yield anything close to 450bhp... Rgds, Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted March 16, 2003 Author Share Posted March 16, 2003 Guesstimate: Stock turbos, or hybrids with stock turbine housings, beyond 400 BHP it's a poor return. You ned to run bigger turbine housings, not easy by any means with the sequential set up. More TURBINE housing sizing housing influenced than exhaust manifold cross section, IMO. Quote Link to comment Share on other sites More sharing options...
Mark Kindell Posted March 16, 2003 Share Posted March 16, 2003 Thats good info again as allways Chris Quote Link to comment Share on other sites More sharing options...
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