what bottom turbo

chrleb1 said:
You need to get a dyno sheet with 800 hp and take it down to Texas for the heck of it. I'm gonna try and complete the truck before November. If you want twins, let's figure it out. Putting a big turbo under that will be slow, but there might be a way to make that SB a little faster. shhhh....
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yeah i will be over at the shop tomorrow and we will talk plus i have to order a few things from ya. that 800hp dyno sheet is coming up buddy. see ya tomorrow.
 
If you run a big set of twins, you could spray it to light it and then run on just the twins once they get going. You will end up only needing one bottle and filling every few trips to the track.
 
I think that a bigger secondary is more efficient for a given primary, and should therefore make more power.

Why? First, a bigger secondary poses less restriction to the flow from the primary. Second, that bigger secondary's turbine will swallow more gasflow, reducing the amount of gas that has to be wastegated around it.

When you hit the spray, you're going to want as much turbine area as you can get on BOTH turbos. That means larger A/R housings than you'd care for on the street to fight lag. That's what you give up to make the big power numbers.

Larger turbos might be overkill for a given HP level, but where they operate on their map will have a huge effect on drive pressure. This is where oversized (biggish) turbos can really pay off. If you have something that's right in the fat part of the middle island or close to it, your drive energy for a given HP can be cut way down.

If you're shooting for big HP on the spray, you gotta have a huge gate on top and/or a large, free-flowing turbine on top. Even the 74mm wheel of a Silver Bullet is too small for a big shot of nitrous. This is where something like a Garrett GT42 on top (82mm wheel) will free up some HP. Yes, it's laggy, but that's the the price for big nitrous HP.

Just like injectors can be optimized for spray or not (mach 8 vs 7), the turbos need to be optimized for the spray as well.

Justin
 
HOHN said:
I think that a bigger secondary is more efficient for a given primary, and should therefore make more power.

Why? First, a bigger secondary poses less restriction to the flow from the primary. Second, that bigger secondary's turbine will swallow more gasflow, reducing the amount of gas that has to be wastegated around it.

When you hit the spray, you're going to want as much turbine area as you can get on BOTH turbos. That means larger A/R housings than you'd care for on the street to fight lag. That's what you give up to make the big power numbers.

Larger turbos might be overkill for a given HP level, but where they operate on their map will have a huge effect on drive pressure. This is where oversized (biggish) turbos can really pay off. If you have something that's right in the fat part of the middle island or close to it, your drive energy for a given HP can be cut way down.

If you're shooting for big HP on the spray, you gotta have a huge gate on top and/or a large, free-flowing turbine on top. Even the 74mm wheel of a Silver Bullet is too small for a big shot of nitrous. This is where something like a Garrett GT42 on top (82mm wheel) will free up some HP. Yes, it's laggy, but that's the the price for big nitrous HP.

Just like injectors can be optimized for spray or not (mach 8 vs 7), the turbos need to be optimized for the spray as well.

Justin
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Justin,

Your theories are correct but real world application and HP leave something to be desired with this setup... The best setup for running nitrous and making HP would be to have a turbo that would spool early and a wastegate that will flow thw pressures off (big internal or even better a larger external wastegate)..... I have used this setup very effectively, get the turbo spooled and the nitrous running it will create a bigger number. Normally I limit the chrgaer to around 75% of what the top of the map shows. This saves the turbo and engine. Fast spoolup and early nitrous compute into a bigger number. If I can have the engine up on boost and the nitrous fully open by 2200-2500 rpm it will produce a much larger number than getting everything open @ 2800-3200 rpm.

Doug
 
You can put the biggest twins on there ever and your still not going to get the # you want out of a vp truck that you can on Nitrous, they just wont deliver the oxygen like spray will, + they would just be a lag monster. You want big #s stay with a single with a large flowing back side.
 
VP trucks, IMHO, don't have the RPM range required to light the big chargers and still make good power. They need the mid size twins, or a decent single and spray...but keep in mind, I've only ever been around 1 600+hp 24v. Working on building a buddy's 02 HO to 500-550, but with Garrett BB twins!

Chris
 
Jetpilot said:
Justin,

Your theories are correct but real world application and HP leave something to be desired with this setup... The best setup for running nitrous and making HP would be to have a turbo that would spool early and a wastegate that will flow thw pressures off (big internal or even better a larger external wastegate)..... I have used this setup very effectively, get the turbo spooled and the nitrous running it will create a bigger number. Normally I limit the chrgaer to around 75% of what the top of the map shows. This saves the turbo and engine. Fast spoolup and early nitrous compute into a bigger number. If I can have the engine up on boost and the nitrous fully open by 2200-2500 rpm it will produce a much larger number than getting everything open @ 2800-3200 rpm.

Doug
Click to expand...

OK, so I see the different reasoning. I was thinking you'd want to capture some of that nitrous heat and use it to light a massive charger and/or allow you to use larger, more efficient housings.

It appears that your reasoning is that you're using the spray in the engine, then just wanting to bleed it off and "get er dun". So you're just lighting a smaller charger, then hitting it with a big shot of squeeze and wastegating off the extra gas to prevent grenading the turbo.

I didn't mean to imply that you'd delay the nitrous until the late RPM range you are mentioning. My point was that nitrous works best with bigger turbos, but you STILL have to get the turbo to light:) I know that some folks use a little spray to help get a bigger charger lit, but this won't work miracles and make a GT45 light as a single:)

I still like the idea of a large hotside with the spray-- it just can't be TOO big. Like I'd go with a Silver model charger over a SPS in a given inducer size. In this case, the Silver would spool a little later (larger wheel), but I would expect the reduction in drive pressure to more than compensate when you hit the button.

NItrous does good things in the engine, but it also has to be able to get out easily or you won't see the full potential.

I suppose it doesn't get much easier than an large external gate wide open.

Thanks for sharing your experience with the *nx* . You've taught me a bunch more than you can imagine.

Justin
 
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