Turbo spool

[Sandaholic]

I am fairly new to turbo diesels so this question is probaly prety lame. Alot of people mention when they are drag racing that they launch with a high level of boost, like with 10# of boost. How are they achieving this type of boost? Are they holding the brake while reving the engine?

[a64pilot]

Yep,
That is exactly what they are doing, pretty much requires an auto trans ;)

[Sandaholic]

So if someone said they launch with 10# would it be the same as saying they launched and 1800rpm or whatever the coresponding psi to rpm is. Since I don't have a boost gauge can rpm be used as a rough gauge of boost?

[chuntag95]

Sandaholic,
Boost is also a function of load on the engine. You can dang near redline and only have a couple of pounds, but you put it in gear and step on it, that's a different story. I don't think every truck will be the same, but should be plus or minus half a hammer handle.

[Jelisfc]

Serious racers will plumb a setup with nitrous to spool the turbo(s) to full boost at a flip of a switch. Not sure how it works plumbing wise but I believe they ignite fuel in or near the turbo to get it to spin.

[king D]

you are gonna need a bigger turbo than the dmax has to need nitrous to make it spool.and as stated every truck is different but at an 1800 rpm launch about were i take off i have no measurable boost ashowing on the gage

[Jelisfc]

King D, when I said serious I meant 4000 hp nitro buring 4 cylinder. Just saw it on TV last week. We're just a wee bit outa their league. :cool:

[a64pilot]

We used to use nitrous on turbo drag bikes for 1 sec until the turbo spooled, you see nitrous is another way to add "air" to an engine. Almost identical effects of a turbo or supercharger, used to call it turbo in a bottle. We weren't using nitrous to spool the turbo, but to add the additional O2 that the turbo would normally be adding. First went for 1 sec time then later used a pressure switch in the intake manifold to disable the NO2. Motor bottom end wouldn't stand both boost and NO2.
BTW by "powerbraking" my truck I can see as much as 15 or so boost, which results in excessive wheelspin, I'm 2wd only, and is probably hell on the drivetrain and results in a slower launch. In my 2wd dooley 10 psi or so seems to be about the max the tires can handle.
I know powerbraking a dooley is silly, But it is a lot of fun :D