Nitrous and a Roots Supercharger

[sneaky98gt]

Ok, I'm more or less thinking out loud here, as none of this will happen until this fall at the earliest. I was discussing future mods with a few other car guys this weekend, and they really got me thinking. This is gonna be long winded, but I hope you guys will read through and tell me what you think.


Short Version

What do you think of a VERY conservatively tuned, SMALL, 50 hp dry shot MAX, on my non-intercooled Eaton setup? I'm not looking to exceed 375 rwhp +/-. Would it be relatively safe?


Tom Clancy Version

So, my car is a street car, plain and simple. For those that don't know, I'm running a stock motor, stock auto transmission, stock rear gears, bolt on, non-intercooled roots-style supercharged car. While it does see the track several times through the year, it's primary purpose is to get me from point A to point B, to the tune of about 20,000 miles per year. While I like to go fast, and I don't mind paying for that, I dislike having to pay for it when I'm NOT going fast. Hence the reason I went with a blower instead of staying NA. Therefore, mods left to do to my car:

1. Gears. Would definitely see a nice gain at the track and in the SOTP meter with a set of 3.73s over the stock 3.27s. However, after doing lots of data collecting, it seems the average MPG loss on the highway when doing that swap is around 3 mpg. That doesn't sound like much, but over the course of 20,000 miles, with gas at $3.25 a gallon, it adds up. Add the installation cost, and we get $750 + $350/year.

2. Cams. Also would see a nice gain. Pretty high parts and labor price considering I'd have to get another tune. Also like gears, I suspect I'd see at least 3 mpg less in fuel mileage. Plus the loss of driveability. Bottom line, I'm looking at $1000 + $400/year and a loss in driveability, no matter how small.

3. Methanol + More Boost. While I'd see a nice 30-40 rwhp bump with no loss in fuel mileage or driveability from this (it would definitely get dyno tuned), I have two problems with doing it. First, the issue of daily driving it. I can either have it tuned to run the meth all the time (which would have me refilling it pretty often, i.e. expensive), or have a separate non-meth tune; the non-meth tune would be cheaper and easier, but I can't imagine 9 pounds of non-intercooled boost (ALL the time) being very friendly (or safe) in the hot summer months. My second problem with the methanol is the safety. If the car is tuned for using the methanol, and the meth system somehow fails, there is no good 'backup' to keep from exploding a few rings and subsequently destroying the motor. That doesn't make me feel very comfortable with it. Assuming I ran the methanol all the time, and it takes 1 gallon per tank of gas, I'm looking at $800 + $500/year.

4. Nitrous. My idea is to run a small (35-50 hp, absolutely no more) dry shot, primarily to cool the ridiculously hot intake charge. I like this because I'd get the same cooling effect of the methanol, but with the added benefit of a few extra oxygen molecules. I don't like the idea of a wet shot because of the risk of backfires, which would probably destroy my blower, plus the fact that a wet kit is more expensive/complicated. I see simplicity as a good thing in my case, and considering all the fuel upgrades I already have, I'm pretty sure a dry shot would satisfy my needs; I also seeing a tuned dry shot being "safe" in that some kind of nitrous system failure wouldn't really hurt anything, other than a decent ET. I'd like to get a confirmation, but I'm pretty sure my 90 mm Lightning MAF, 39 pound Cobra injectors, and SVT Focus fuel pump would provide enough fuel for a small shot. I would get a very, VERY conservative tune for the nitrous, which would ONLY be used at the track a few times a year, and leave my other (current) tune alone. This would leave my mileage and driveability untouched and exactly where I want it. Going by other people's estimates, one bottle would probably last me two track trips, which would amount to a generous $200/year in nitrous. Add the parts and tune, and I get $750 + $200/year.


What I want you guy's input on:
1. From the fuel mileage, driveability, SOTP meter, fun/$ aspects, would you choose the nitrous as well? From here on out, I'll assume you do.

2. Wet or dry? Is my above reasoning for getting a dry kit logical?

3. Are my 39 pound injectors, 90 mm MAF, and Focus pump enough for a 50 hp shot on top of my current setup?

4. What kind of power gains do you think I'd get with a 50 hp shot? Is a safe 50 rwhp possible? What kind of torque numbers would it make? 450+ rwtq? Considering that it would combine cooling and the extra oxygen, I think that it would be possible to get 75 rwhp out of a 50 hp shot, but I'd have it tuned way back down for safety's sake.

Finally, and most importantly, Safety.

What are your thoughts on the safety? Some places I've read say to go for it, but most people are like, "ZOMG you are totally gonna blow the motor if you even attempt that!!!! Forget it!!!" The problem with them is that I'm 99% sure they are assuming you're already running 9+ pounds of boost, already making 380+ rwhp, you're not going to tune it, and are going to spray a 125 hp shot on top of that. Well, yes, duh, it's not gonna last. In my situation, I'm talking a small, VERY conservatively TUNED, 50 hp MAX shot. 375 rwhp +/-. Which would only be used a few times a year anyway. Is 375 rwhp on a lower boost supercharged/nitrous car really any more dangerous than a 375 rwhp higher boost supercharged only car? I can't see why it would be. But maybe I'm misinformed. Inform me.

Torque. What are the limits of the stock motor in terms of torque? I suspect I'd make more than I'd think I would. Definitely 400+. Is that safe on a stock motor?

Bottom line
Nitrous Pros
1. Cheapest initial cost
2. Cheapest running cost
3. Best driveability situation
4. Best fuel mileage situation
5. Most power
6. "Safe" in that the consequences for a failure are small.

Nitrous Cons
1. Will the motor hold it....?
2. I know I'll probably want to pill it up sooner or later....


And I think that's it. Let me know your thoughts on this, even if you don't know anything about it. Looking to get a discussion going that will talk me into or out of my current little fad, and for the info of future inquirers (considering I couldn't find any good info on it).

 

[Winters98GT]

HAHA. You basically wrote an article, Will!

3. Methanol + More Boost. While I'd see a nice 30-40 rwhp bump with no loss in fuel mileage or driveability from this (it would definitely get dyno tuned), I have two problems with doing it. First, the issue of daily driving it. I can either have it tuned to run the meth all the time (which would have me refilling it pretty often, i.e. expensive), or have a separate non-meth tune; the non-meth tune would be cheaper and easier, but I can't imagine 9 pounds of non-intercooled boost (ALL the time) being very friendly (or safe) in the hot summer months. My second problem with the methanol is the safety. If the car is tuned for using the methanol, and the meth system somehow fails, there is no good 'backup' to keep from exploding a few rings and subsequently destroying the motor. That doesn't make me feel very comfortable with it. Assuming I ran the methanol all the time, and it takes 1 gallon per tank of gas, I'm looking at $800 + $500/year.

Will, Meth is a safety feature, not something to be concerned with. A lot of things can go wrong, sure the pump can fail. You can use a lot of safety features, and your tuner can tune in to the meth for power or safety. I have my car about half and half. I use it for a little power, but also as a safety measure. We gained 60rwhp/80rwtq with it. I have a little light that turns red when the system is armed under load, then turns green when spraying. It is set at like 4-5psi, and only turns on under heavy load. I could an entire year, even using a little boost, and not use a drop of meth if I didn't want to. Meth injection is not a constant thing.

Also, I would look in to the effects of spraying it in to the blower with the impellers spinning that fast. I have never seen somebody spray a roots blower(though I am sure a lot of people do) with meth. I would probably opt for a dual system with small jets so that the mist is much smaller particals when it hits the impellers, if it is even safe to do.

I know very little about spraying nitrous with a blower, or really even nitrous. Sounds like a good idea for the track, with little effect on your daily commute.

 

[sneaky98gt]

HAHA. You basically wrote an article, Will!

Hence this:

Tom Clancy Version

I'm loading up with info in hopes that someone will find it useful in the future.

Will, Meth is a safety feature, not something to be concerned with. A lot of things can go wrong, sure the pump can fail. You can use a lot of safety features, and your tuner can tune in to the meth for power or safety. I have my car about half and half. I use it for a little power, but also as a safety measure. We gained 60rwhp/80rwtq with it. I have a little light that turns red when the system is armed under load, then turns green when spraying. It is set at like 4-5psi, and only turns on under heavy load. I could an entire year, even using a little boost, and not use a drop of meth if I didn't want to. Meth injection is not a constant thing.

Yea, that's kinda what I was thinking with the meth; just don't tune it too aggressively. I'm just worried that the power it will make won't be worth the money and complexity it will cost.

On that note, I've been talking to some of the guys over on the TCCoA (one of which is running the exact setup I am, less than an hour away). A LOT of them run the methanol with the roots blowers, so I assume that it's ok to do.

Also something else that I knew a while back, but forgot about: the IAT sensor. It is currently still in the stock location in the intake tube behind the MAF, before the blower. Because it's pre-blower, it can't measure the temps of the outlet side of the blower and adjust timing accordingly. Therefore, a lot of the SVO blower guys relocate it to the actual blower itself. There, it can measure the temps accurately and pull timing if necessary. This would sure make me feel a little more comfortable about failures of the meth system. If it were to fail, with the IAT sensor relocated, it would (in theory) sense the higher temps and pull timing accordingly.

What kit are you running? Progressive or single stage?

I know very little about spraying nitrous with a blower, or really even nitrous. Sounds like a good idea for the track, with little effect on your daily commute.

I don't either. Which is why I was asking. Definitely don't want to dive into something without knowing all the ins and outs of it.

 

[GDawg]

Tom Clancy version!

I'll have to read this a couple times!

Are you sure you have 3.27 gear? I would think for the auto you would have 3.08. And I would go with 4.10s.

 

[Winters98GT]

I am running East Coast Supercharging's single Alky system. However, my meth kit is not read by the IAT either. Mine is behind my MAF, and I did not relocate the IAT. Some guys do, that run multiple stages and dual nozzles. My meth motor is at my left foot inside the fenderwell(outside the cab). Not only is the light right there when it sprays, buy you can hear it turn on and actually hear it spraying(stock exhaust, minus mufflers).

My tune gives me a little room since it is not maxed out on timing. I would bet you can gain 30/50 with a safe tune, and if the kit fails, your motor will still be fine if the tune is spot on and you realize it is not spraying with safety features.

I love meth. My car went from 131 to 135-136 just with it and it hits like a small shot at WOT at around 3000rpm. I can still take my car to right under 4k under light-moderate load without the system kicking in, which I love for daily driving.

 

[bhuff30]

I played with meth for a little while, but I was actually disappointed with the power gain. Maybe I just didn't have it tuned well for the meth. Sounds like it worked very well for winters though. I completely agree though, keep the tune safe for pump gas without meth, and use meth to add a margin of safety. It generally won't add a lot of power in that setup though.

I have played with nitrous and boost and I quite enjoy the combination. I would definitely recommend a wet shot instead of a dry shot. The dry shot adds fuel by increasing the fuel pressure and/or tricking the ACT sensor into thinking it is colder so add more fuel. When you are boosting, your fuel pressure increases above base to compensate for the boost also. So by the time you combine a dry shot and boost, the fuel pressure will be getting pretty high, possibly higher than most pumps could deal with. What's more, if the pump starts getting weak, it will show more severely in that situation.

You were worried about a nitrous back fire, but that will generally only occur if you spray a large shot and fuel starts puddling. Where your air charge temps are high from boost, it won't be so likely to puddle... especially with a small shot. If you spray it, make sure to get all the good safety equipment. I'd say a window switch to keep you safe on the rev limiter and when bogged down.

I spray a 35 shot on my 2.3 and gained .7second and 4-5mph. On a boosted car, you can easily gain more than the rated shot.

 

[sneaky98gt]

Tom Clancy version!

I'll have to read this a couple times!

Are you sure you have 3.27 gear? I would think for the auto you would have 3.08. And I would go with 4.10s.

I'm positive I have 3.27s. That's what the tag on the differential says, and I get 3 and a quarter turns of the drive shaft for one turn of the wheel.

4.10s would put me at not even 112 mph at 6000 rpm. The calculator I used And it would KILL my mileage.

I played with meth for a little while, but I was actually disappointed with the power gain. Maybe I just didn't have it tuned well for the meth. Sounds like it worked very well for winters though. I completely agree though, keep the tune safe for pump gas without meth, and use meth to add a margin of safety. It generally won't add a lot of power in that setup though.

Yea, that's kinda my biggest problem with the meth. I'm sure that there are gains to be had, and I suspect the more power you're making, the more you'll gain. I'm just not convinced that the cost and complexity it will add to my setup will be worth the power it will net.

I have played with nitrous and boost and I quite enjoy the combination. I would definitely recommend a wet shot instead of a dry shot. The dry shot adds fuel by increasing the fuel pressure and/or tricking the ACT sensor into thinking it is colder so add more fuel. When you are boosting, your fuel pressure increases above base to compensate for the boost also. So by the time you combine a dry shot and boost, the fuel pressure will be getting pretty high, possibly higher than most pumps could deal with. What's more, if the pump starts getting weak, it will show more severely in that situation.

You were worried about a nitrous back fire, but that will generally only occur if you spray a large shot and fuel starts puddling. Where your air charge temps are high from boost, it won't be so likely to puddle... especially with a small shot. If you spray it, make sure to get all the good safety equipment. I'd say a window switch to keep you safe on the rev limiter and when bogged down.

I spray a 35 shot on my 2.3 and gained .7second and 4-5mph. On a boosted car, you can easily gain more than the rated shot.

I'm still not decided on the wet-dry question yet. I'm gonna talk to a few more folks in my area, along with a couple of tuners, and see what they say before I decide.

I'm definitely going to have all the safety stuff. If I were to do this, I'm going to use the Harris Speed Works kit, as well as their nitrous controller (window switch). I'm also probably going to install a wideband, and use the controller to kill the nitrous if the AFR goes too lean. I want this to be as safe as possible.

I'd be ecstatic over a .7 second gain. Although I don't doubt it's possible. The biggest gains for me would be in getting it out of the hole much more quickly.

 

[bhuff30]

I was spraying from the line, so most of the .7 seconds gained was in the 60'. With just the turbo, I was having trouble getting the boost up on the launch, so the best I could do was 2.0 60' times. After adding the 35 shot, the car would get moving on the nitrous shot, then spool the turbo hard and fast just moments after leaving. That instantly dropped me to low 1.8's and high 1.7's.

The only concern I would have spraying from the line in your case is the tight factory torque converter. It only stalls to ~1500 when you stomp the gas from a stop, right? Spraying from 1500, you will really have to keep the shot size small. It isn't that terrible though, because soon as you spray, the converter will slip more because of the extra torque. My 2.3 stalls to ~2500 without boost, about 3000 on boost and about 3800 on nitrous and boost. So you would get up to 2000 pretty quickly before anything really bad could happen.

I'd be ecstatic over a .7 second gain. Although I don't doubt it's possible. The biggest gains for me would be in getting it out of the hole much more quickly.

 

[sneaky98gt]

I was spraying from the line, so most of the .7 seconds gained was in the 60'. With just the turbo, I was having trouble getting the boost up on the launch, so the best I could do was 2.0 60' times. After adding the 35 shot, the car would get moving on the nitrous shot, then spool the turbo hard and fast just moments after leaving. That instantly dropped me to low 1.8's and high 1.7's.

The only concern I would have spraying from the line in your case is the tight factory torque converter. It only stalls to ~1500 when you stomp the gas from a stop, right? Spraying from 1500, you will really have to keep the shot size small. It isn't that terrible though, because soon as you spray, the converter will slip more because of the extra torque. My 2.3 stalls to ~2500 without boost, about 3000 on boost and about 3800 on nitrous and boost. So you would get up to 2000 pretty quickly before anything really bad could happen.

It stalls a little closer to 2000 rpm. At the track, I've had the best results by launching at 17-1800.

I know my tires would never hold the torque a nitrous shot makes out of the hole. My plan was to spray it as low as possible and still maintain traction and safety (another reason I'm leaning towards dry, being able to spray lower). I was thinking that 2500 rpm sounds reasonable. That should allow the car to hook and really get the weight transferred before the nitrous hit. Hopefully, that would allow solid 1.7 60's.

What kind of extra torque would a 50 hp shot make at 2500 rpm? 100 ft lbs?

 

[bhuff30]

Sounds like a good plan. Yeah, a 50 shot would add just a little more than 100 ft*lbs at 2500. But you also have to keep in mind the torque converter multiples torque when you are moving slowly, so the gain to the wheels could be higher until you gain a little more speed.

It stalls a little closer to 2000 rpm. At the track, I've had the best results by launching at 17-1800.

I know my tires would never hold the torque a nitrous shot makes out of the hole. My plan was to spray it as low as possible and still maintain traction and safety (another reason I'm leaning towards dry, being able to spray lower). I was thinking that 2500 rpm sounds reasonable. That should allow the car to hook and really get the weight transferred before the nitrous hit. Hopefully, that would allow solid 1.7 60's.

What kind of extra torque would a 50 hp shot make at 2500 rpm? 100 ft lbs?

 

[sneaky98gt]

Just got back from my tuner. I asked him all this stuff that was on my mind, he told me to throw the nitrous idea out. He said that I could definitely do it, and that it would make really good power, but that he'd never feel comfortable tuning it on a stock bottom end.

He said more boost and meth was the way to go. It'd make more power, and the meth would only make it safer. With the IAT relocated, he said he could tune it for use with the meth and make pretty good power, but still have it to where it'd pull timing and keep it safe it something were to go wrong. He suggested a stage 1 Snow kit and have it come in around 3 pounds of boost. That would keep me from using any when daily driving. It also comes with a low level indicator and a light for when it's spraying.

He said 40 rwhp should be pretty easy with 3 more pounds of boost and meth, with at least that much more torque. Considering that that's about what I'm looking for, I guess that's not so bad. They also had the Snow kits for MUCH cheaper than I've seen them listed before, and they would cut me a discount on the tune because I've had them tune for me before. All in all, it'd be less than $500 all said and done. Not too bad, I guess.

 

[Winters98GT]

Sounds good, Will.

I'd go with a dual nozzle setup, I wish I had on mine.

 

[sneaky98gt]

Sounds good, Will.

I'd go with a dual nozzle setup, I wish I had on mine.

What's the advantage in that? Will it benefit a car making as little power as mine?


Oh, and I love the new quote in your sig.

 

[Winters98GT]

What's the advantage in that? Will it benefit a car making as little power as mine?


Oh, and I love the new quote in your sig.

Yeah, I thought it was halarious. It one from one of the threads on an LS site where shops are making 800-850rwhp now on stock ls3's. Pretty applicable to anybody running boost regardless of power. They all take the plung sooner or later, some in 10k, others with 150k.

From my understanding, the dual nozzles shoot a finer mist, and it gets a more even circulation in to each cylinder. Some people and shops disregard that idea, but some of the top shops with the fastest cars only go with a dual setup for safety and performance purposes. It is not going to cost you that much more. I'm def. switching over soon. A guy here in Houston gained 125rwhp from just meth in his stock bottom ls2(728rwhp), and is only at 10.8:1 A/F up top, and has a ton of power left in it.

This is what meth did for me. I am completely hooked on the stuff. I know exactly how much throttle to add to get in to boost without using any meth. Mine is set at like 4psi but also has to do with how far I push down on the gas, and I have a bit of timing I could have added to get another 10-20hp. I gained 5mph at the track with it. I also only added .5 pounds of boost. With 3psi and meth, I'd guess you would pick up 50-60rwhp(Im winters"97gt" on other sites)

I was a big skeptic and scared of all the "what ifs" before I added the system. Not anymore. If the motor blows, it is my fault for not making sure the green light in front of my face was on for the meth, or it was just time. I feel that meth is a win/win for me.

What is your shop saying about spraying anything in to the blower that is wet? Those impellors are turning very fast in there, that might be the one thing that would worry me with a roots blower.

 

[Winters98GT]

Not the SVO blower, but here is something I remember skimming over but not reading since it didn't apply to me.

Meth on twin screw? - Corvette Forum

Things are either abrasive, or they are not. The pressure won't turn a non abrasive fluid into an abrasive all of a sudden.
Back when I worked at a Nuclear Power plant, the 5000+ Horsepower reactor coolant recirculation pumps used hydrodynamic bearings to support the pump shaft; these were 3 steel plates stacked up on top of one another with 1000PSI of water pressure in between them; the plates spun extremely close to one another under enormous loads surpported by only that thin film of water. The water caused no abrasion since those seals had a service life of more than 10 years.
The issue with the coating is not abrasion; it is chemical resistance. The coating is epoxy based and Methanol breaks down most epoxies. 100% water injection may be a safer solution on these blowers.

Also, as a side note, injecting a liquid into a roots blower will increase its volumetric efficiency since the liquid improves rotor to rotor and rotor to casing seal, as per Corky Bell's "Supercharged!" book.

 

[sneaky98gt]

Crazy numbers, man. Why did the other guy gain over 100 hp vs. your 60 hp? Intercooler?

And the dual nozzles upgrade is only like $30 more with the Snow kit. I'll definitely run that by Caleb and see what he says.

I'm feeling pretty confident that my tuner actually feels my car will make a lot more power with the spray and a pulley. He first told me not to bother with it, that it wouldn't make power under 350 rwhp, but when I reminded him I didn't (and couldn't) have an intercooler, he said that it would definitely be worth it. With the methanol and extra boost, he said he could make 40 more hp more safe than my current power levels, so that has me feeling pretty good about it.

I definitely want to do this sometime. It's just a matter of prioritizing all my money for the next school year first, and making sure I've got a plenty extra to spend. If I wind up with a decent job/co-op this summer/fall (pretty high chances I will), this will probably be done the middle of this summer.

 

[sneaky98gt]

Not the SVO blower, but here is something I remember skimming over but not reading since it didn't apply to me.

Meth on twin screw? - Corvette Forum

Good info there. I'm not sure either how those blowers would compare to the M112 I have. I do know that a lot of the guys on the TCCoA and SCCoA have run meth with these blowers for quite some time now. Not saying that that means it's safe, but it has been done by some guys with some record setting SVO supercharged cars for over 10 years now.

 

[Winters98GT]

He has a little more efficient blower than me, and he cranked up the boost and meth. Guy is nuts. He self tuned his car at the shop I use, and the owner told him that he had "big brass ones" when he was on the dyno. The car is still in one peice and is a beast.

Most tuners won't do that, because it jeopardizes their reputation when the car blows up soon after, so they tune in to the meth a bit to make more power while still using some of the safety qualities of meth.

Looking forward to seeing what your car does with it! I know you will really enjoy it!

 

[Winters98GT]

Good info there. I'm not sure either how those blowers would compare to the M112 I have. I do know that a lot of the guys on the TCCoA and SCCoA have run meth with these blowers for quite some time now. Not saying that that means it's safe, but it has been done by some guys with some record setting SVO supercharged cars for over 10 years now.

Those guys know there stuff then. I just thought I would play devils advocate since I don't have a lot of experience with it. I would go with the TCCoA guys, they always had sound advice when I read their threads.