Chris Wilson Posted February 22, 2004 Share Posted February 22, 2004 I have received some e-mails regarding turbo primary pipe design and sizing, integral V external wastegates, and post turbo pipe sizing, so the below may also be of more general interest: It's too long to post here, but those wanting to see this (and be warned, it's techie and only of interest to die hard modders) can download it form my web site HERE Quote Link to comment Share on other sites More sharing options...
dandan Posted February 22, 2004 Share Posted February 22, 2004 Thanks Chris, makes interesting reading. With regard to many of our cars on here (typically: full decat, exhaust, 1.2-1.3bar etc with around 360-380 at the hubs) with max power of say 400-420 at the crank, are we likely to be losing out slightly with a 2.5" top decat pipe? I know there are many issues with accurate boost control from the wastegate in our particular turbo setup resulting in the need for restrictor rings. Hence the line of thinking that 2.5" is more than large enough as boost spikes are already occuring and causing problems. However, are we losing out here at all? Do you think that a 3" top pipe combined with a reliable wastegate (eg enlarged orifice and button as on many hybrids) would yield any gains on its own over a 2.5" pipe, at these higher power levels? This is purely out of interest as I'm well aware of many other areas where my £££ is better invested, performance wise, at these relatively moderate power levels. Thanks Dan Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 22, 2004 Author Share Posted February 22, 2004 No, even at 1.2 bar you are pushing the edge of the stock turbos boost window, it's really not working at all efficiently. No advantage at all will come from a 3 inch downpipe. I know this as when i first developed my downpipe kit on my own Supra, years ago, i built a 3 inch set up, and did back to back tests, with no power gain at all, given the same boost figures. You need to address the tiny turbine sizing before worrying about bigger downpipes, thes are the stumbling block for stock turbos and why I, personally, consider hybrids a waste of time. Just adding a bigger compressor section on the stock turbine is never going to do much save raise cylinder combustion temps even higher. What gets rammed in needs to flow out, and as the turbine sections of the TT are bespoke, unique castings without sufficient material in them for maching out (assuming such an intricate operation were even viable), means such mods remain theoretical. It's why i have ALWAYS said beyond basic mods people need to decide whether to take the big jump to a programmable ECU and a single turbo or none sequential twins. Given freedom of choice regarding all aspects of turbo sizing, and cam selection freedom to suit them, the power world is your oyster. The engine was designed, totally successfully, to offer a fabulous compromise of low end grunt with very acceptable high rpm power, with instant spool. Such was the slant towards these aims, however, mods are limited very severely by those turbine housings and the gas velocity encouraging tiny primary manifold runner sizes, and the tame cam timing needed to stop exhaust gas reversion at the mega high exhaust back pressures induced. Quote Link to comment Share on other sites More sharing options...
dandan Posted February 22, 2004 Share Posted February 22, 2004 Thanks Chris, I appreciate totally your point on hybrids with regard to the extreme restriction in the turbine area and the fight against high exh manifold pressures and reversion. As you say the initial design aim of a highly driveable performance car (via the seq system) is a cracking design. We are all pushing the performance envelope and forcing this system to cope with power outputs never envisaged to begin with. The results will of course be high egt's and diminishinig returns in performance gains. Personally I think I'm approaching the limit of the system and bar a few reliability modifications (FMIC, oil cooler, new clutch, egt gauge and fuel pump) I'm done for now and more than happy with the performance. Again, interesting reading Chris Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted February 22, 2004 Share Posted February 22, 2004 Chris, I thought that your De-Cat pipes came in different dimensions for the UK and J-Spec. Is this true or am I just a pissed up monkey???? Surely a 3" pipe with a restristor ring, used at the start would be better than using a lower dimensioned pipe and then having to upgrade the whole system later on for those die hard people with big singles in mind etc etc. Do you do a different spec for both the jap and UK derived versions?? Ben.. Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted February 22, 2004 Share Posted February 22, 2004 I'm a monkey - Forget this post!! Ben.. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 22, 2004 Author Share Posted February 22, 2004 Originally posted by Soonto"HAS"soop Chris, I thought that your De-Cat pipes came in different dimensions for the UK and J-Spec. Is this true or am I just a pissed up monkey???? Surely a 3" pipe with a restristor ring, used at the start would be better than using a lower dimensioned pipe and then having to upgrade the whole system later on for those die hard people with big singles in mind etc etc. Do you do a different spec for both the jap and UK derived versions?? Ben.. Pipes are same diameter, the flange at the turbo end is totally different on UK cars though. If you change to a single the downpipe will be useless anyway, as it's almost bound to need a totally different configuration. Quote Link to comment Share on other sites More sharing options...
eyefi Posted February 22, 2004 Share Posted February 22, 2004 nice bit of writing, very "entertaining" one thing i have been thinking about, is the angle of the seperate wg pipe. should it still stay at 90deg to the wastegate hole? the wg valve when fully open is at about 45deg (if that), what effect does this have on the gas flow? surely it would rather follow the deflected angle rather than straight on? another point would b, what diam would the wg pipes b? Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted February 22, 2004 Share Posted February 22, 2004 Originally posted by Chris Wilson Pipes are same diameter, the flange at the turbo end is totally different on UK cars though. If you change to a single the downpipe will be useless anyway, as it's almost bound to need a totally different configuration. So when you supplied me a set of UK pipes when my De-Cat pipes went to south wales, was the first De-Cat pipe a UK or a J-Spec?? I ain't bothered either way, just not sure what I got?? What's the difference between the two? Ben.. Quote Link to comment Share on other sites More sharing options...
Justin Posted February 22, 2004 Share Posted February 22, 2004 Originally posted by Chris Wilson I, personally, consider hybrids a waste of time. Just adding a bigger compressor section on the stock turbine is never going to do much save raise cylinder combustion temps even higher. What gets rammed in needs to flow out, and as the turbine sections of the TT are bespoke, unique castings without sufficient material in them for maching out (assuming such an intricate operation were even viable), means such mods remain theoretical. It's why i have ALWAYS said beyond basic mods people need to decide whether to take the big jump to a programmable ECU and a single turbo or none sequential twins. Given freedom of choice regarding all aspects of turbo sizing, and cam selection freedom to suit them, the power world is your oyster. . But Chris I think there are two things to be considered why people here go for Hybrids: 1. They are a fix for broken J-Spec tubbies 2. They are cheap compared to a new ECU, single turbo kit and much higher insurance premium. If you only have £2000 - £2500 to repair/upgrade your turbo set-up what options do you have?? It annoys me that if/when my turbos go I have little option that will ever give me back the spool up and performance that Toyota did Always good to read your input Chris. Much appreciated. Justin Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 22, 2004 Author Share Posted February 22, 2004 Justin, there is no reason not to have worn turbos rebuilt to stock size, compressor wise, although, AFAIK, there is no UK company offering a rebuild with ceramic turbine wheel. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 22, 2004 Author Share Posted February 22, 2004 Originally posted by eyefi nice bit of writing, very "entertaining" one thing i have been thinking about, is the angle of the seperate wg pipe. should it still stay at 90deg to the wastegate hole? the wg valve when fully open is at about 45deg (if that), what effect does this have on the gas flow? surely it would rather follow the deflected angle rather than straight on? another point would b, what diam would the wg pipes b? Measure the area under the valve in the new wastegate, fully opn (basic maths, diameter and lift needed), and if the pipe is a bit bigger it will be fine. Whilst altering the angle to match flow direction is ideal, it may not be practical, and probably doesn't matter such will be level of flow asked of it. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 22, 2004 Author Share Posted February 22, 2004 Originally posted by Soonto"HAS"soop So when you supplied me a set of UK pipes when my De-Cat pipes went to south wales, was the first De-Cat pipe a UK or a J-Spec?? I ain't bothered either way, just not sure what I got?? What's the difference between the two? Ben.. Not sure now, can't remember to be honest! The UK first pipe has a much bigger flange where it fastens to the 3 studs on the turbo elbow casting. Quote Link to comment Share on other sites More sharing options...
Soonto_HAS_soop Posted February 22, 2004 Share Posted February 22, 2004 As I said previously Chris, I ain't bothered either way, but what differenece is there between the two in regards to size (mm)? Ben.. Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted February 23, 2004 Share Posted February 23, 2004 just been reading on supraforums about 4" downpipes and midpipes for single kits. they are having a bit of arguments about them. a maker of the 4" pipes saying he made 140 hp from going from 3" to 4" pipes. i have had a few different pipes on my car blitz 3" mid pipe 3" full decat pipe replacing both cats. boosted to 1.5 bar and it did feel mad now got both cw 2.5" pipes and restrictor ring in TTC mode seems to be at about 1.3 bar Quote Link to comment Share on other sites More sharing options...
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