What RPM does your turbo start building boost?

Craash

Craash

Registered
I have a K11 with a new RCC kit, with pistons, valves, water injection, springs, etc. I make a total of ~11 pounds of boost.

It made 279 HP on a 103 degree day.

The turbo starts building boost at around 6K or so, and gets nasty quick. By 9K there is 250 HP to the ground.

It's alot of fun on the stock wheel base (rear -4). The only thing I wish I could change was to bring the boost in sooner.

I had it out tonight - the first cool night we've had in a while - and while coming down an on ramp I ran the RPM up to 9.5K or so in first gear at about 1/2 throttle. I short shifted and grabbed wide open throttle in 2nd only to have the front end 12 oclock and the rear drift nicely to the right leaving a blackie. I backed out of it a bit, let the rear grab and carried the front end the rest of the way down the ramp. I'm sure I looked goofy with my ear to ear smile.

When does your turbo start to build noticable boost, and how much HP are you putting down?

IMG_7700-Small.jpg
 
Craash said:
I'm running spring pressure only at this point. 11.x pounds.

A boost controller isn't going to help you make boost any lower in the rpm range.
Click to expand...

Actually it can.

With an 11lb spring on your setup, probably not. However when running lighter springs or larger wastegates; a boost controller that adds preassure to the top of the gate will help keep the gate from cracking open and bleeding off boost prior to attaining peak boost. Therefore allowing you to use all of your exhaust flow/pressure/energy to spin the turbine.

For instance; if you run a 6lb spring and datalog the bike, then put in a 12lb spring. The turbo will build 6lbs of boost at a lower RPM. This is due to the gate being held closed longer.

I don't know how evident this would be on a smaller turbo such as a TO4E. But on larger GT35 and 40s its pretty standout.
 
I should have clarified my question a bit better. I'd like my boost to hit at a lower RPM so that when crusing in a non-boosted maner you don't have to drop as many gears (or reach as high of an rpm) to obtain boost. I don't think a controller will help here.

It's my understanding this is maily a function of the turbo itself.

crawler said:
Actually it can.

With an 11lb spring on your setup, probably not. However when running lighter springs or larger wastegates; a boost controller that adds preassure to the top of the gate will help keep the gate from cracking open and bleeding off boost prior to attaining peak boost. Therefore allowing you to use all of your exhaust flow/pressure/energy to spin the turbine.

For instance; if you run a 6lb spring and datalog the bike, then put in a 12lb spring. The turbo will build 6lbs of boost at a lower RPM. This is due to the gate being held closed longer.

I don't know how evident this would be on a smaller turbo such as a TO4E. But on larger GT35 and 40s its pretty standout.
Click to expand...
 
Craash said:
I should have clarified my question a bit better. I'd like my boost to hit at a lower RPM so that when crusing in a non-boosted maner you don't have to drop as many gears (or reach as high of an rpm) to obtain boost. I don't think a controller will help here.

It's my understanding this is maily a function of the turbo itself.
Click to expand...

As far as what you're wanting, you're now dealing with the nature of a turbo. Smaller turbo or turbine housing would spool faster, however you would be sacrificing efficiency and top end power. Tuning can play a part, timing added/removed in different RPM ranges will affect the spooling characteristics. (Smithers probably did a fine job, not doubting them) I'm just speaking in broad strokes.

Turbo specific camshafts, cam degree-ing, a small shot of NO2 would all be possibilities.

But at this point that would all require pulling the topend down and a re-tune.
 
crawler said:
As far as what you're wanting, you're now dealing with the nature of a turbo. Smaller turbo or turbine housing would spool faster, however you would be sacrificing efficiency and top end power. Tuning can play a part, timing added/removed in different RPM ranges will affect the spooling characteristics. (Smithers probably did a fine job, not doubting them) I'm just speaking in broad strokes.

Turbo specific camshafts, cam degree-ing, a small shot of NO2 would all be possibilities.

But at this point that would all require pulling the topend down and a re-tune.
Click to expand...

That's pretty much my thoughts on it too. I suppose the best solution would be to drive in the 'powerband' of the bike - we are talking about 279 HP.
 
I start seeing boost on the boost gauge about 3500 rpm. it's not really noticeable until about 4500-5000 rom. putting down 270 Hp.
 
I have 270hp, and my boost starts to come on hard at 5- 5 1/2k I have low compression pistons as well. Out of boost it almost feels sluggish compared to stock, then once it hits hold on!
 
Craash said:
That's pretty much my thoughts on it too. I suppose the best solution would be to drive in the 'powerband' of the bike - we are talking about 279 HP.
Click to expand...

Is your kit the one Frank ordered with the larger turbine housing? If so that is why the boost comes in later, larger turbine housing = more peak power, but slower spool time, your turbine housing is a .63 a/r, typical one we send out is a .48 a/r, the .48 will show positive boost around 3500 rpm and hit target pressure by 6000 rpm

Richard
 
I'm sure I'm the one, Richard. Guess I should have researched it a bit more first!

Still, overall a great kit, I just wish it had more down low(er).
 
Sell your turbo kit and put a supercharger on it if you want low end power. Welcome to turbos. You could also change your gearing. Perhaps go up a tooth on the front sprocket. More load on the motor brings the power on a tad sooner.
 
Murderedout07 said:
Sell your turbo kit and put a supercharger on it if you want low end power. Welcome to turbos. You could also change your gearing. Perhaps go up a tooth on the front sprocket. More load on the motor brings the power on a tad sooner.
Click to expand...

My front is already an 18 (stock on gen2), and I'm down 2 in the back for close to the same effect. Don't get me wrong . . . I love the power it makes.
 
I have a gt4094. If I remember correctly it might be building a small amount of boost by 6500 but nothing happens till 7500-8k. I've ridden smaller turbos and wanted more on the top and then there ate days where I rode mine and wished for quicker spool. I'm having some work done on my bike and getting it retuned within the next month or so. Originally made 600+ but the plan now is to make use of the ams1000 and perfect the pump tune. I'm runnin a 240 on the rear but I will probably see 360-400 at the wheel just depends on the dyne I guess
 
I run 11.5:1 CP Pistons, boost starts to build at 3500 - 4000K. At 6 lbs. of boost I have 254 HP at 9 lbs I have 288 hp.

The higher compression helps the turbo spool up faster and I can get away with less boost. The turbo is a Velocity Stage one with two stages of boost the second stage being adjustable.
 
i start building boost at 3k, i run a t-28, small turbo, i still run the stock oil cooler.....:grinning:
 
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