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The big wheel conversion on the K04 doesn't have the same flow rate as the larger turbos but the larger turbos also add lag. It is up to each owner to draw the line on how much lag they are willing to live with - my personal thought is that while higher peak power may be exhilarating right after you get it; living with more lag may annoy you forever after, so I tend to the somewhat conservative regarding turbo flow.
Anyone have a lead on actual dyno numbers for the various turbos? I agree that power isn't as useful, if it is only made in a very limited range. I would much rather have power on demand throughout the rpms, than a high peak that takes forever to reach. I have limited experience with turbos, but the stock K04 feels as though lag is nearly non-existent and I would hate to sacrifice that quality in pursuit of a number. However, I would hope that the "Big Wheel Turbo" would also have the same qualities, while providing a bit more power.
 

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The big wheel set up gives you another 60 bhp, given an appropriate tune and that is very obvious when you put your foot down. The lag is only slightly more than the stock K04 has (which as you say is negligible).

Beware of bhp claims - dynos read differently and people wanting to sell things will use figures from one of the 'generous' dynamometers. The only really useful dyno numbers are those taken before and after on the same dyno on days with very similar temps and weather.

This might be of interest Differences between dyno #'s: Dynojet, Dynapack, Mustang.
 

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The big wheel set up gives you another 60 bhp, given an appropriate tune and that is very obvious when you put your foot down. The lag is only slightly more than the stock K04 has (which as you say is negligible).

Beware of bhp claims - dynos read differently and people wanting to sell things will use figures from one of the 'generous' dynamometers. The only really useful dyno numbers are those taken before and after on the same dyno on days with very similar temps and weather.

This might be of interest Differences between dyno #'s: Dynojet, Dynapack, Mustang.
I have read that you can achieve a max of 320hp crank. With the big wheel and a tune which is about 20 over the ko4.
 

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Sbindley achieved 324 at the wheels with the big wheel. That approximates 370 at the crank. You usually see 240 or so at the wheels on a stock car.
 

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Sbindley achieved 324 at the wheels with the big wheel. That approximates 370 at the crank.
I would sure like to know more about how this was done- no way I can get there on 92 octane without knock.
 

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I would sure like to know more about how this was done- no way I can get there on 92 octane without knock.
Here is a quote from a respected forum member that may partially explain it:
Beware of bhp claims - dynos read differently and people wanting to sell things will use figures from one of the 'generous' dynamometers. The only really useful dyno numbers are those taken before and after on the same dyno on days with very similar temps and weather.
 

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Sbindley achieved 324 at the wheels with the big wheel. That approximates 370 at the crank. You usually see 240 or so at the wheels on a stock car.
Matched flow between the compressor and turbine will typically give you better overall performance. Larger compressor wheel may achieve better flow during part of the rpm range and lose it in others. Increasing compressor wheel size introduces higher load on the turbine which causes an increase in exhaust restriction and a decrease in boost pressure capability. Think of it as the turbine has less leverage to spin the larger compressor wheel. It basically changes the efficiency curve.
 

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Here is the thread on one of the first conversions using that turbo.

 

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Here is the thread on one of the first conversions using that turbo.

Note that that the wheel wasn't the only change.
 

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Yes, he made several changes, but the only one that adds any power (other than the turbo) was the high flow cat.

FYI, for people wanting times, another member I carried on a conversation with by PM did the same thing. He managed to get the car down to a 12.9 1/4 time and a year or so later I recall him telling me he had got it just under 12.8. No ide what tires etc. he was using to do that.
 
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