Lee P Posted September 26, 2009 Share Posted September 26, 2009 (edited) Not exactly, the turbos start producing boost very low down the rev range but take longer to reach max boost pressure. With a single turbo the boost is acheived quicker so the power comes in alot harder which gives you the neck snapping feeling. Its all about power delivery and the twins are smoother and more linear in the way they come on boost. A very large single turbo will be laggy but all the boost will still come in at once. Sorry I am not quite as good at putting things into words as you guys but I am trying. Hmm. Obviously the twins don't affect mechanical or aerodynamic grip at all, so the only way it could even slightly affect grip is by how much power is fed to the wheels and how quickly. To avoid unsticking the tyres you have to gently introduce the power. Feeding power to the rear wheels slowly is also known as "boost lag". A "linear power band" is generated when the turbos take a long time to spin up to boost, also know as lag. Not spinning the wheels in 1st and 2nd is, well, because the turbos never really get on song. Because there isn't enough load to get them spun up. Also known as, mmm, lag. See where I'm going with this? I'm willing to see a nice dyno chart and hear arguments to say otherwise though -Ian Edited September 26, 2009 by Lee P (see edit history) Quote Link to comment Share on other sites More sharing options...
Chingy Posted September 26, 2009 Share Posted September 26, 2009 The advantage of twins over single is traction. After borrowing your car this week I agree, both mine and yours running similar power, but yours feels alot more usable on the road with a smoother power delivery and no wheel spinning in 4th Quote Link to comment Share on other sites More sharing options...
a98pmalcolm Posted September 26, 2009 Share Posted September 26, 2009 have a look http://www.pistonheads.co.uk/sales/1235203.htm Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 (edited) Not spinning the wheels in 1st and 2nd is, well, because the turbos never really get on song. Because there isn't enough load to get them spun up. Also known as, mmm, lag. See where I'm going with this? I'm willing to see a nice dyno chart and hear arguments to say otherwise though -Ian Well here is a video of me and Chingy at , my car does quite well considering the turbos apparently dont really "come on song" in first or second gear Edited September 26, 2009 by Lee P (see edit history) Quote Link to comment Share on other sites More sharing options...
DODGYDODDS Posted September 26, 2009 Share Posted September 26, 2009 have a look http://www.pistonheads.co.uk/sales/1235203.htm very nice, what a sweet engine bay. Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 Well here is a video of me and Chingy at , my car does quite well considering the turbos apparently dont really "come on song" in first or second gear I know 1st gear is a mess with a T67 and 2nd gear gives the traction control a hernia sorting it out, and that's at the region of late 500/early 600bhp depending on the mood and the alignment of the planets. I get nowhere near 1.4bar in those two gears, and even 3rd can cause the RLTC to chip in in the dry, thus limiting the boost. It chirps away throughout the powerband as well, so it's not just a sudden 'shock' of the turbo coming on I can't see you getting full boost in 1st or 2nd either, which is what I meant by "getting on song". You must have a dyno graph or something to show the power curve surely I can't really understand a turbo coming on quickly with a substantial amount of boost and then slowly increasing to full pressure unless you've got boost creep or mad wastegate control haha. Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 (edited) This is the best example I can give you. The top graph is a single turbo which gives you a sudden spike in power. The second graph is a HKS Twin kit which is much more gradule (linear), hence the better traction. I know the graphs are scaled differently but it still shows the difference. I have added my graph to the bottom as it has a torque curve and shows the smoother power delivery better. Edited September 26, 2009 by Lee P (see edit history) Quote Link to comment Share on other sites More sharing options...
jevansio Posted September 26, 2009 Share Posted September 26, 2009 I quickly put the previous 2 graphs into a spreadsheet to compare them directly, make of it what you will. Single = blue, twins = pink (not my colour choice, excels ) Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 Jev, your graph doesn't work my man, you go up to 9000rpm I'm crunching some numbers here, will post again in a mo. -Ian Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 Jev, your graph doesn't work my man, you go up to 9000rpm I'm crunching some numbers here, will post again in a mo. -Ian Would be good to compare the torque cuves if possible. Quote Link to comment Share on other sites More sharing options...
jevansio Posted September 26, 2009 Share Posted September 26, 2009 Jev, your graph doesn't work my man, you go up to 9000rpm I'm crunching some numbers here, will post again in a mo. -Ian Ian, the numbers aren't rpms, they're just indexes, as it goes they start at 3000rpm and go up in 500's so 1 = 3000, 2 = 3500 and so on Quote Link to comment Share on other sites More sharing options...
Chingy Posted September 26, 2009 Share Posted September 26, 2009 Well here is a video of me and Chingy at , my car does quite well considering the turbos apparently dont really "come on song" in first or second gear was on your wheels then, give me those drag radials and we'll go again Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 OK right, don't shoot me for this, but I've taken the three graphs shown and taken the power values off them at 500rpm points, chucked the numbers into excel, and produced the attached graph. I've also attached the excel sheet for you to look at if you doubt my numbers but I included them in the screenie. Everything is rounded to +/- about 10bhp because obviously I'm working off graph pictures and some of the scales are annoyingly odd on the Doluk one. But the numbers are big enough to survive such variance without affecting the overall result. Erm what can I say. In the nicest possible way, I know which car I'd rather drive... Again don't shoot me, they are your numbers I could do the torque curves but seeing as the single has 350ft/lbs while the twins are struggling to reach triple figures I really don't think it'll change the results much. The single has a much much larger 'area under the curve', it's got masses of power from 4000rpm+ so would be lovely and driveable. It's only the last 1000 rpm that the twins catch up. While having impressive headline power figures, they're maybe just too big a set of tubbies for the engine/rev limit I'm going to have to stick by my conclusion that you don't lose traction because the turbos are laggy Standard disclaimer applies of course, if you're happy with your car then who cares - have you drive of the Doluck car though? -Iansinglevstwincomparison.xls Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 Just realised the Doluck is yours, Chingy Nice motor, I've compared your graph to one of mine, T67 vs T04Z, pretty much the same curve, about 30bhp difference here and there. They are quite similar turbos I believe. Plenty of oomph from 3500rpm onwards I expect sir -Ian Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 The problem is that my graph does not give an accurate representaion of when the boost actually come in because on the road it is 5000rpm. Colin can varify this as he has driven it. Ignore the late power, it still shows a more progressive power delivery. Trust me both cars drive completely differently and having experienced both, the point was that my car was more drivable as it wasnt spinning the wheels in the first 4 gears like the do luck car. Even though they are just as quick as each other as proven on the track at Santapod. Colins is much more fun though. Quote Link to comment Share on other sites More sharing options...
dandan Posted September 26, 2009 Share Posted September 26, 2009 Interesting graph - no great suprise. Something to bear in mind though....if a traction control system is working overtime and pulling back the torque due to a lack of grip then dyno graphs don't make for the fairest comparison of road going performance.... Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 Thanks for the effort of puting the graphs together Ian Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 Interesting graph - no great suprise. Something to bear in mind though....if a traction control system is working overtime and pulling back the torque due to a lack of grip then dyno graphs don't make for the fairest comparison of road going performance.... Well yeah, you have a point there, and one that's mostly stopped any questing for more power by myself. Having it cutting in 3rd gear (it's not mental or intrusive, just an audible 'misfire' as it cuts injectors) = about 70/80mph. I've got Pirelli P0's on there, not Nankang Ditchfinders, so really, is there any need for more power that is useless until I'm in 4th at 100mph? I can't see there is. I wouldn't downsize to a T61 because that raw shove is awesome, but I wouldn't want anything laggier... Quote Link to comment Share on other sites More sharing options...
Ian C Posted September 26, 2009 Share Posted September 26, 2009 Thanks for the effort of puting the graphs together Ian No probs I love this stuff, I hope I didn't tread on toes Quote Link to comment Share on other sites More sharing options...
dandan Posted September 26, 2009 Share Posted September 26, 2009 Well yeah, you have a point there, and one that's mostly stopped any questing for more power by myself. Having it cutting in 3rd gear (it's not mental or intrusive, just an audible 'misfire' as it cuts injectors) = about 70/80mph. I've got Pirelli P0's on there, not Nankang Ditchfinders, so really, is there any need for more power that is useless until I'm in 4th at 100mph? I can't see there is. I wouldn't downsize to a T61 because that raw shove is awesome, but I wouldn't want anything laggier... That's the kind of logic I went with to end up with my choice of a 67mm turbo. Quote Link to comment Share on other sites More sharing options...
Chingy Posted September 26, 2009 Share Posted September 26, 2009 [ATTACH]99060[/ATTACH] -Ian Great comparison, good findings looking at that Just realised the Doluck is yours, Chingy Nice motor, I've compared your graph to one of mine, T67 vs T04Z, pretty much the same curve, about 30bhp difference here and there. They are quite similar turbos I believe. Plenty of oomph from 3500rpm onwards I expect sir -Ian Thanks buddy, just looked at your garage awesome looking car, love that second picture Your graph is very very similar, great torque figure Quote Link to comment Share on other sites More sharing options...
tDR Posted September 26, 2009 Share Posted September 26, 2009 Meh... HKS Twins aren't even as fast as stock twins... Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 No probs I love this stuff, I hope I didn't tread on toes Of course not, its just really difficault to show in the graphs what the car is actually doing on the road. Being lucky enough to have driven both cars we can give our descriptions of how they drive and perform but showing it on paper is hard. I will have to take you for a spin Ian so you can see what we mean. Quote Link to comment Share on other sites More sharing options...
Lee P Posted September 26, 2009 Share Posted September 26, 2009 Meh... HKS Twins aren't even as fast as stock twins... Let me borrow your gearbox and we will see Quote Link to comment Share on other sites More sharing options...
dandan Posted September 26, 2009 Share Posted September 26, 2009 Of course not, its just really difficault to show in the graphs what the car is actually doing on the road. Being lucky enough to have driven both cars we can give our descriptions of how they drive and perform but showing it on paper is hard. I will have to take you for a spin Ian so you can see what we mean. A couple of 40-90 and 70-140 runs would be an awesome comparison...come on fellas Quote Link to comment Share on other sites More sharing options...
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