Flavio Posted April 8, 2002 Share Posted April 8, 2002 After fitting my stock exhaust a couple of weeks ago after having sold my HKS Hiper Carbon I immediately noticed an increase in low end torque. I cannot figure this out. I am a layman but I always thought that the less back pressure the turbo had the faster the exhaust gases could flow and therefore the faster the power could come, i.e. more torque at lower rpm's. I am sure Lord Mycroft can explain the error in my theory. Flavio http://www.mkivsupras.co.uk/ (Edited by Flavio at 10:24 pm on April 8, 2002) Link to comment Share on other sites More sharing options...
Guest Mycroft Posted April 8, 2002 Share Posted April 8, 2002 I can, yes. Link to comment Share on other sites More sharing options...
Flavio Posted April 8, 2002 Author Share Posted April 8, 2002 So tell me then! Flavio Link to comment Share on other sites More sharing options...
Guest Ash Posted April 8, 2002 Share Posted April 8, 2002 As I said on another post... a good book on the topic is: Fundamentals of Heat and Mass Transfer, 4th edition ISBN 0-471-30460-3. Yours, J Hey, Doc, I just noticed you changed your footnote. C'mon my friend, it don't suit if I may say. The other one was more apt. (Edited by Ash at 9:56 pm on April 8, 2002) Link to comment Share on other sites More sharing options...
Guest Martin F Posted April 8, 2002 Share Posted April 8, 2002 Quote: from Mycroft on 9:27 pm on April 8, 2002[br]I can, yes. Hey Flavio i think our Lord of the Soararse's wants you to beg for the info! Link to comment Share on other sites More sharing options...
Guest Mycroft Posted April 8, 2002 Share Posted April 8, 2002 Explaining Exhaust design is not simple and trying to precis it into something 'manageable' takes time. I neither need or want to be 'begged' for this info, I need and want time to precis. In the mean time, if CW or anyone else has the info to hand in a straight forward form then please post it! Link to comment Share on other sites More sharing options...
Doughie Posted April 8, 2002 Share Posted April 8, 2002 Hypothesise. Link to comment Share on other sites More sharing options...
Guest Mycroft Posted April 9, 2002 Share Posted April 9, 2002 Put simply, fully efficient torque developement from turbo'd cars is partially a product of heat, not the main 'plug' of torque (which is just filling the chambers) just the full exploitation, if the exhaust gases leave the head too quickly (which happens in a high flow exhaust) then engine is termed as running cold at lower RPM, (just as the terminology in spark Plugs) run it too cold and the torque generation efficiency is decreased. The fall off is not very great but it is does blunt the performance. Most good designs of exhaust are tuned to mitigate this problem, it is at its worst around 2k to 3k by restriting the flow of the gases, this makes the head hotter and more efficient gaining a bit back at this rev band. Kakimoto Exhausts have the best design for this, their 'twin-leaf' design works very well at keeping the head hot at low revs and yet does not choke the the high rev 'clearing' so essential for not generating too much heat causing the BHP to drop at higher revs. The exhaust I designed for my Soarer is based on the Kakimoto design principle. That is it in precis'd form, Ash is right if you want to delve deeper the Book he has mentioned will help and if you can get them the Yamaha/Kakimoto Exhaust design CD's are VERY good and not just show you how to design your own ('S' level maths is handy) but also good reference works are on them too, 3CD's, if you can find a set! Link to comment Share on other sites More sharing options...
Guest Mycroft Posted April 9, 2002 Share Posted April 9, 2002 That is why I don't understand why so many Supra owners put super free flowing exhausts on their cars, the 3ltr is a TORQUE generating monster! I would have no truck with free-flowing this and that but look toward something that got the most out of the engine DESIGN. Your engines are not 'screamers' they are 'thunderers'. Link to comment Share on other sites More sharing options...
Adam W Posted April 9, 2002 Share Posted April 9, 2002 Errrm, mainly for the cool noise it makes! There's no point having a moster of a car if it sounds like a sewing machine at WOT. What about if you put a really short, 3" unsilenced exhaust exiting behind the front wheel somewhere (ie about 2.5' in length) - would that do horrific things to the driveability/power delivery? Link to comment Share on other sites More sharing options...
Guest Mycroft Posted April 9, 2002 Share Posted April 9, 2002 But you can have both! Lovely thunder, with basso profundo rumbles and linear (more) power delivery with better throttle responses. Link to comment Share on other sites More sharing options...
Phil Wall Posted April 9, 2002 Share Posted April 9, 2002 OK that sounds like perfection, how do I get it? Link to comment Share on other sites More sharing options...
Adam W Posted April 9, 2002 Share Posted April 9, 2002 No Phil, perfection would be all that AND two foot flames on every gear change Mmmmmm . . . . attention seeker? Moi? Link to comment Share on other sites More sharing options...
Flipfinger Posted April 9, 2002 Share Posted April 9, 2002 And a Mad Max-a-like burble at tickover for me please. Link to comment Share on other sites More sharing options...
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