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600 BHP - Which is quicker, Single or Twin?


suprastu

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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 by Lee P (see edit history)
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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 :p Edited by Lee P (see edit history)
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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 :p

 

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 :shrug:

 

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.

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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.

 

 

image

image

 

image

Edited by Lee P (see edit history)
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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 :shrug: Standard disclaimer applies of course, if you're happy with your car then who cares - have you drive of the Doluck car though?

 

-Ian

singlevstwincomparison.jpg

singlevstwincomparison.xls

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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 :salute:

 

-Ian

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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. :D

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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...

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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. :)

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[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 :salute:

 

-Ian

 

Thanks buddy, just looked at your garage awesome looking car, love that second picture :)

 

Your graph is very very similar, great torque figure

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No probs I love this stuff, I hope I didn't tread on toes :scare:

 

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. :)

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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 :D

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