How much boost is to much boost??

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How much boost is to much boost?? #1571837 30/04/2016 18:32 30/04/2016 18:32
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	I was talking about boost levels to mapper at Surry Rolling Road the other week and i said most of us more powerful coupes are under 2 bar of boost and some people have this image of high boost heros etc as a bad thing so my question to the forum today is How much boost is to much boost? and what sort of power (including good power band) should people be seeing at what level. also if you look at some of the other tuned engines out there (evo, Audi 5 pot, ford YB etc) alot of them are running up past the 3 bar mark with rev limits in some cases at 10k RPM and making high reliable power with massive broard power curves. I may of open a can of worms but i do like a good debate Last edited by knight7660; 30/04/2016 18:40. LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

Re: How much boost is to much boost?? [Re: knight7660] #1571857 30/04/2016 22:31 30/04/2016 22:31
Joined: Dec 2005 Posts: 17,367 Staffordshire Nigel Forum veteran
Nigel Forum veteran Joined: Dec 2005 Posts: 17,367 Staffordshire	I'm mapped for 1.6 bar, but I find 1.4 bar is a decent everyday setting A few years ago, I was mapped for 2.1 bar and race fuel and it was utterly ballistic, but violent to drive - huge fun when in the mood, but just too frantic for the road. I now prefer the "grunty" feel of relatively modest boost, but still with no tail-off of boost at the top end, thanks to a hefty turbo I'm guessing that 2+ bar is easier to handle when the rear wheels (or all four) are being driven....

Re: How much boost is to much boost?? [Re: knight7660] #1571872 01/05/2016 06:05 01/05/2016 06:05
D DorianStiglic Unregistered
DorianStiglic Unregistered D	power band is not related with turbo pressure, some larger turbo will give more power with less boost for example original turbo on 16v max is 250hp with t4 compressor it goes on 380hp on same boost on 16v engine is hard to get big power band because cams are fixed if you want more power you need more aggressive cams and than you need a turbo with bigger turbine ar and bigger compressor ar power band can be achieved with twin scroll turbocharger witch spools up on lower revs. not always car with more hp will be faster if you are pushing standard turbocharger above efficiency it will just create more heat not more power and you will kill the turbo sooner, yes it can make 2,8bar boost but it will heat air so much that you want be able to cool it down

Re: How much boost is to much boost?? [Re: knight7660] #1571876 01/05/2016 09:04 01/05/2016 09:04
B Brickfoot Unregistered
Brickfoot Unregistered B	Too much boost is exactly at the level that destroys your engine Jokes aside, as saidits all down to theturbochsrger and what its built to do.. A 250 hp turbocharger is built for good spool, midrange etc and will produce a lot of heat and backpreassure at higher boost/power. If you strap a gtx40 to the thing you could probbably boost north of 3 bar on a built motor with the right parts and the right tune.. But not really usable (or sain) on a fwd coupe.. 1,5 bar on that thing would probbably make twice the power of 1,5 bar on an 60trim T3.. Oooooh the compromises

Re: How much boost is to much boost?? [Re: knight7660] #1571881 01/05/2016 10:13 01/05/2016 10:13
Joined: Jul 2012 Posts: 1,650 Dark side of the Moon H_R My life on the forum
H_R My life on the forum Joined: Jul 2012 Posts: 1,650 Dark side of the Moon	Don't forget the block and internals are the biggest limiting factor!

Re: How much boost is to much boost?? [Re: knight7660] #1572242 03/05/2016 20:30 03/05/2016 20:30
S suba Unregistered
suba Unregistered S	How much boost you can run safely depends on the overall setup and tune of the car: 1. Turbo (standard TB28 turbo with more than 1.2 bar just kicks out heat, and wont last long - going higher does not give more power, but you are far more likely to melt a piston due to charge temps if you are pushing the car for sustained periods. 2. Compression ratio - The cosworth YB and EVO run low compression, which means more boost and less likely to detonate - more on/off feel to the boost threshold 3. Rev limit - standard rod bolts on the 20vt become the limit first, then valve springs - at 10,000 you will put a rod through the block. 4. the bigger you go on the turbo, the more boost you can run at lower temps, but then the threshold is higher, so you have to compensate with a higher rev limit to get the powerband. This still does not help you on the road, where realistically for a fast road car you should have positive boost around 3-3,500 rpm 5. The bigger the turbo, the more unrestricted flow you need, i.e. 4 inch exhaust, external wastegate, 5 stud turbo to downpipe, higher lift cams, etc. it all comes down to how much you want to spend, and balancing driveability with power. if you you need is a 3K power band for doing 1/4's that's fine - go for that, but the car will be a pig on the road, or on most tracks. There's a lot more info there if you choose to get really stuck in, but that is the gist of it. I'd challenge anyone taking a stock evo or Cosworth YB and slapping 3 bar through it at 10K rpm without a lot of supporting mods...

Re: How much boost is to much boost?? [Re: ] #1572308 04/05/2016 10:36 04/05/2016 10:36
Joined: Dec 2005 Posts: 12,295 Sandhurst Begbie Ex El Presidente
Begbie Ex El Presidente I AM a Coop Joined: Dec 2005 Posts: 12,295 Sandhurst	Originally Posted By: suba 2. Compression ratio - The cosworth YB and EVO run low compression, which means more boost and less likely to detonate - more on/off feel to the boost threshold EVO's actually run higher CR than the coupe. Most of the time it's 8.5/1 - 9/1, whereas YB's tend to go lower to 7/1. I wouldn't quite agree with the on/off threshold though. Mine is 7/1 and it's actually quite nice for spooling / threshold. Whereas the Juke RS that I've got as well, is higher CR and when left in 'sport' mode, that kicks in more on the threshold, plus, it feels laggier, but then again, I am comparing a 1.6 200bhp to a 2.0 435bhp Originally Posted by Jonny - After being taken out at Spa Your car is Usain Bolt with wellies

Re: How much boost is to much boost?? [Re: Begbie] #1572346 04/05/2016 13:44 04/05/2016 13:44
S suba Unregistered
suba Unregistered S	Begbie's a better encyclopaedia than me. Must be that fancy Guy Croft flow work.

Re: How much boost is to much boost?? [Re: knight7660] #1572424 05/05/2016 10:23 05/05/2016 10:23
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	sorry guys been away so havent seen the replys but catching back up now LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

Re: How much boost is to much boost?? [Re: Nigel] #1572425 05/05/2016 10:26 05/05/2016 10:26
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	Originally Posted By: Nigel I'm mapped for 1.6 bar, but I find 1.4 bar is a decent everyday setting A few years ago, I was mapped for 2.1 bar and race fuel and it was utterly ballistic, but violent to drive - huge fun when in the mood, but just too frantic for the road. I now prefer the "grunty" feel of relatively modest boost, but still with no tail-off of boost at the top end, thanks to a hefty turbo I'm guessing that 2+ bar is easier to handle when the rear wheels (or all four) are being driven.... The 2+ boost can be mapped to be more easier to handle though ie boost per gear and Rpm so wouldnt that be something ever to consider think of having all that power but have the drivablity at the same time LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

Re: How much boost is to much boost?? [Re: ] #1572428 05/05/2016 10:45 05/05/2016 10:45
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	Originally Posted By: suba Begbie's a better encyclopaedia than me. Must be that fancy Guy Croft flow work. yes begbie's 16vt is a highly worked beast but is there anything which can be changed to improve the over all power etc this is without spending a small fortune getting stroker kits involved. unless theres a cheaper stroker kit i havent seen. I know bigger turbos make more power with less boost etc but this is why i was saying about higher rev limits to make use of the power band of a bigger turbo which unlike my 2871 tails off after 7200rpm LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

Re: How much boost is to much boost?? [Re: ] #1572429 05/05/2016 10:50 05/05/2016 10:50
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	Originally Posted By: suba How much boost you can run safely depends on the overall setup and tune of the car: 1. Turbo (standard TB28 turbo with more than 1.2 bar just kicks out heat, and wont last long - going higher does not give more power, but you are far more likely to melt a piston due to charge temps if you are pushing the car for sustained periods. 2. Compression ratio - The cosworth YB and EVO run low compression, which means more boost and less likely to detonate - more on/off feel to the boost threshold 3. Rev limit - standard rod bolts on the 20vt become the limit first, then valve springs - at 10,000 you will put a rod through the block. 4. the bigger you go on the turbo, the more boost you can run at lower temps, but then the threshold is higher, so you have to compensate with a higher rev limit to get the powerband. This still does not help you on the road, where realistically for a fast road car you should have positive boost around 3-3,500 rpm 5. The bigger the turbo, the more unrestricted flow you need, i.e. 4 inch exhaust, external wastegate, 5 stud turbo to downpipe, higher lift cams, etc. it all comes down to how much you want to spend, and balancing driveability with power. if you you need is a 3K power band for doing 1/4's that's fine - go for that, but the car will be a pig on the road, or on most tracks. There's a lot more info there if you choose to get really stuck in, but that is the gist of it. I'd challenge anyone taking a stock evo or Cosworth YB and slapping 3 bar through it at 10K rpm without a lot of supporting mods... I am talking about forged lumps as a base not stock because we all know roughly what there good for. LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

Re: How much boost is to much boost?? [Re: knight7660] #1572452 05/05/2016 14:27 05/05/2016 14:27
S suba Unregistered
suba Unregistered S	have a search on Nyssa7 on here - there have been a few threads on rev limits on the 20VT in the past, and he's pushed the limits on a track.

Re: How much boost is to much boost?? [Re: knight7660] #1572461 05/05/2016 15:05 05/05/2016 15:05
Joined: Dec 2007 Posts: 2,252 Windsor/ Reading knight7660 OP Competition Level
knight7660 OP Competition Level Joined: Dec 2007 Posts: 2,252 Windsor/ Reading	well Biggends was playing in the zone of 8200rpm safely so with some uprated valve springs etc should be able to push abit more. Last edited by knight7660; 05/05/2016 15:05. LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7

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