Undersized turbo/pre-turbo nitrous injection gains?

Totally don't know why I'm posting this in 3800 land. Just because that's where things go, I guess.

So I've been doing the usual over-thinking/math about increasing mass flow through a turbo(s) at the limit of what the turbo will deliver. Specifically, trying to figure out how much more I could squeeze out of the stock turbos on the Mercedes because upgrading them is simply not an option (for multiple reasons...it's an engine out job, more than 850hp requires a $15,000 standalone computer because there's supposedly no adjustment any of the tuners have access to to scale injectors in an S600 computer, everything involved is enormously expensive).

Basically, I was trying to figure out exactly how much mass flow increase you get through a turbocharger from the vaporization cooling out of a wet nitrous shot (propane on the fuel side) at a ratio of around 27% of your non-nitrous horsepower in terms of the shot size. That's 200hp on top of 750 worth of non-nitrous airflow. Anybody else want to struggle with the math on that to verify my findings? This is with the assumption that the turbo is absolutely maxxed out, boost falling off, and it's already been intercooled to the max so the temperature change has no effect on power apart from mass flow through the compressor. It may end up putting a little more to the ground from VE/pumping loss changes as well, but with the compressor as the limiting factor it shouldn't matter how easily the engine breathes...if it takes in more air, it would just be at less psi and due to choke flow at the outlet, turbos flow the most air mass at mid to higher pressures, usually 1/2 to 3/4 the way up their chart. So reducing boost pressure through intercooling or other means that make the engine more efficient would not have a positive effect on the absolute mass flow the turbo could deliver. The ONLY way left to increase power out of these bad boys would be by improving air density at the compressor inlet. Water/meth cannot do this to significantly low temperatures so despite helping shift the map a little bit due to wet compression, but cannot do so to the extent of a 70-100 degree F inlet temp drop that a nitrous/propane combo can provide.

I come up with around a 14% inlet density improvement if you vaporize all the nitrous and propane before it hits the turbo, but the nitrous/propane combo displaces around 10% of the air mass in doing so for a net mass flow gain of around 4% and a net hp gain of the nitrous shot plus that 4% applied to the pre-nitrous horsepower. In this case that's 750 base HP * 1.04 = 780hp plus the 200 shot of nitrous = 980hp. Which is a shame because I'd love to call it an even 1000. The 4% was a very complicated and recursive calculation overall so I don't want to go into it here, but does that sound about correct? 30hp of free/incidental power on top of a 200 shot? I KNOW that it would be a lot more if the nitrous functioned as intercooling and the turbo was maintaining a set boost, but that's not what I want to know for the following reasons:

I know I've seen people claim crazy gains from this over and above the nitrous shot size, but I think that's often due to the turbo being on a boost controller, not running all out...so obviously colder charge air is going to result in a lot more air mass at the same boost pressure IF the turbo can deliver it. But if your compressor is maxxed out, it's a different story and that's the situation I am trying to predict. These will be absolutely off the map on the screaming edge probably with no wastegating before I even think about adding the nitrous.

Does anyone have real-world results of a similar situation? By that, I mean spraying nitrous through a turbo that was small enough to not be able to maintain the peak boost in the upper rpms. Most likely a stock turbo on some car or other that was on the bottle? I would need to know the shot size, the horsepower without it, and the horsepower with it, and it would have to have been sprayed pre-compressor. I'm not interested in incidental intercooling gains, the math on that is easy enough. I want to know the net effect on air density vs total new volume...which I have come to believe is around 10% at that 27% of horsepower shot sizing (and the propane is something like 1.5% of that, so probably 8.5% on the nitrous alone).
 
I did/do have concerns about nitrous backfires with that combination. But I ran the numbers and the propane by volume at max load would be around 1% by volume. The Lean flammability limit is 2.1% by volume, so assuming I wasn't spraying at low rpms, it's no significant increase in terms of backfire hazard vs nitrous by itself. That's good reason to not run the propane jetting overly rich though.
 

Mr_Roboto

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Uh, If fuel is your big issue with the turbo system then why not add an extra injector like they used to do old school style? Not optimal but an option.

What about bigger turbos+methanol injection? I would want some kind of safety interlock before I did this probably but supposedly you can get 20%ish on top of a fuel system if you're pushing it. Something else to consider is can you change the compressors without it being an engine out operation? May be worth consideration. Then again maybe not.

$15K seems stupid expensive for an ECU to be hacked. You could easily have a Motec or BS3 thrown in for that kinda coin.

If you end up doing nitrous/propane I'd be VERY curious about how you managed it and ensured fuel system consistency. I was toying with the idea a long time ago and what I came up with was cyrogenic regulators or using a bottle heater/pressure transducer similar to a nitrous bottle. Even with the cryo regulator a heater may be required depending on tank size, demand and driving temps. I was actually wanting to use the propane with an air to liquid intercooler similar to an A/C evaporator. Jay Carter in the Buick performance arena used to sell a propane kit but it was vape only. Jesus it's been fucking years since I've talked with him.
 
Uh, If fuel is your big issue with the turbo system then why not add an extra injector like they used to do old school style? Not optimal but an option.

Fuel is not an issue as of yet, I was just stating that in order to get a significant gain even by upgrading turbos, I would have to go to an aftermarket ECU. The limitation prior to that is that supposedly these stock turbos are all out of steam at just shy of 700hp.

What about bigger turbos+methanol injection? I would want some kind of safety interlock before I did this probably but supposedly you can get 20%ish on top of a fuel system if you're pushing it. Something else to consider is can you change the compressors without it being an engine out operation? May be worth consideration. Then again maybe not.


$15K seems stupid expensive for an ECU to be hacked. You could easily have a Motec or BS3 thrown in for that kinda coin.

I have water/meth in the intake manifold already for knock control/charge cooling as well as E85 primary fuel (which I had to just measure stock injector flow rate and order appropriately oversized injectors in order to do since supposedly the injector scaling in the computer cannot be changed). Pre-turbo water/meth is on my immediate to-do list in order to shift the compressor map a bit and try and get some more out of it, but the big issue with that is the 90-degree compressor inlet. Anything I spray will have to make a turn, and if the air temps are low-ish at all, some of it is going to stick to the walls and potentially cause issues as it rolls toward the compressor as a large drop. So I'm going to keep the injection amount very low.

As far as the ECU is concerned, the reason they are ridiculously expensive is all the integration that needs to take place. The computer talks to about a hundred other computers in the car and if you don't have an aftermarket ECU that will play nice with all of them, you lose all kinds of features (suspension issues, climate control issues, literally countless other systems). It could possibly be worked around, but I sure don't want to try and figure it out.

If you end up doing nitrous/propane I'd be VERY curious about how you managed it and ensured fuel system consistency. I was toying with the idea a long time ago and what I came up with was cyrogenic regulators or using a bottle heater/pressure transducer similar to a nitrous bottle. Even with the cryo regulator a heater may be required depending on tank size, demand and driving temps. I was actually wanting to use the propane with an air to liquid intercooler similar to an A/C evaporator. Jay Carter in the Buick performance arena used to sell a propane kit but it was vape only. Jesus it's been fucking years since I've talked with him.

Twin push setup regulated from the same high pressure argon bottle. Nitrous in one bottle, propane in the other. Check valves in each bottle to facilitate high pressure bottle replacement (to allow much smaller volume bottles to be used and changed more frequently), and prevent the two from ever mixing before injected. Nitrous solenoids on both due to the pressure. Will have to work out the jetting on some sacrificial test mule with a wideband. Essentially, set the pressure at 1100psi or something that should keep the nitrous liquid to a bit over 100 degrees F ambient so that nothing is ever boiling in the bottle to maintain pressure. This also eliminates the need for a bottle heater because the bottles won't get cold...nothing has to evaporate in them to maintain pressure. Route and insulate lines well away from any heat other than ambient to prevent boiling/gas bubbles in the line. Pretty well as guaranteed as it gets to always deliver both as liquid at a perfectly consistent ratio since it's the same feed pressure. Only need to purge the first time you open the valve. The trick is, you've got to run fairly large nitrous jetting to get a small enough orifice for the propane side to maintain the right AFR. Since normally the fuel side is 50psi or something and you're injecting at 1100psi. So basically you have no choice but to go big to a certain extent. The solution for that might be a progressive controller if you didn't want to run a 100+shot or whatever it works out to. I forget the exact math.
 
I was actually wanting to use the propane with an air to liquid intercooler similar to an A/C evaporator. Jay Carter in the Buick performance arena used to sell a propane kit but it was vape only. Jesus it's been fucking years since I've talked with him.

Did you mean sacrificial propane, or as freon in a contained system? I actually am currently using propane as refrigerant in the A/C system based intercooler chiller on my twincharged Buick. -44 beats the hell out of -15. It'll fog the windows too in the summer. Lol.
 
I forgot to address the turbo compressor wheel upgrade suggestion. Definitely not possible in-car either. The compressor covers are held on with 6 impossible to remove bolts (well, at least about 4 of them per side are). I attempted to remove them to drill holes for water/meth injectors, but gave up after about 6 hours. I mean the engine has to come completely out to change motor mounts on this thing. Everything is insanely tight.

I don't think I would want to just slap the billet compressor wheels on there without having the assembly rebalanced anyway even if I could get at them. Something about 100s of thousands of rpms makes me worry about balance a lot with turbos.
 

Mr_Roboto

Doing the jobs nobody wants to
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I have water/meth in the intake manifold already for knock control/charge cooling as well as E85 primary fuel (which I had to just measure stock injector flow rate and order appropriately oversized injectors in order to do since supposedly the injector scaling in the computer cannot be changed). Pre-turbo water/meth is on my immediate to-do list in order to shift the compressor map a bit and try and get some more out of it, but the big issue with that is the 90-degree compressor inlet. Anything I spray will have to make a turn, and if the air temps are low-ish at all, some of it is going to stick to the walls and potentially cause issues as it rolls toward the compressor as a large drop. So I'm going to keep the injection amount very low.

Trying to "flex" the map a bit makes a lot of sense. As a question what about building a tube with a nozzle on the end of it that has a 90 on it? Yeah I realize that disrupts air flow a bit but it may be worth it in the long run. Either that or some in car crazyness if you can stuff a rag in the inlet, drill/tap a hole and vacuum the shavings out. Would certainly not be the first time it's been done.

As far as the ECU is concerned, the reason they are ridiculously expensive is all the integration that needs to take place. The computer talks to about a hundred other computers in the car and if you don't have an aftermarket ECU that will play nice with all of them, you lose all kinds of features (suspension issues, climate control issues, literally countless other systems). It could possibly be worked around, but I sure don't want to try and figure it out.

That's why I suggested the Motec first. Supposedly they have a huge amount of integration even shit like DBW.


Twin push setup regulated from the same high pressure argon bottle. Nitrous in one bottle, propane in the other. Check valves in each bottle to facilitate high pressure bottle replacement (to allow much smaller volume bottles to be used and changed more frequently), and prevent the two from ever mixing before injected. Nitrous solenoids on both due to the pressure. Will have to work out the jetting on some sacrificial test mule with a wideband. Essentially, set the pressure at 1100psi or something that should keep the nitrous liquid to a bit over 100 degrees F ambient so that nothing is ever boiling in the bottle to maintain pressure. This also eliminates the need for a bottle heater because the bottles won't get cold...nothing has to evaporate in them to maintain pressure. Route and insulate lines well away from any heat other than ambient to prevent boiling/gas bubbles in the line. Pretty well as guaranteed as it gets to always deliver both as liquid at a perfectly consistent ratio since it's the same feed pressure. Only need to purge the first time you open the valve. The trick is, you've got to run fairly large nitrous jetting to get a small enough orifice for the propane side to maintain the right AFR. Since normally the fuel side is 50psi or something and you're injecting at 1100psi. So basically you have no choice but to go big to a certain extent. The solution for that might be a progressive controller if you didn't want to run a 100+shot or whatever it works out to. I forget the exact math.

The one (albeit untested) flaw of this idea is I believe you could end up dissolving the inert gas into the propane like CO2 into a soda which is typically done at 15ish PSI. That's why I was reluctant to work on something along those lines as I would be afraid it would cause a less than steady AFR as more inert gas absorbed into the LPG. Jetting shouldn't be bad with what's in the aftermarket I'd be looking for 150-200 PSI on the propane side just because that's likely where you'll end up on a hot day with a fullish tank. There are enough nitrous jets out there you should be able to figure something out.

Did you mean sacrificial propane, or as freon in a contained system? I actually am currently using propane as refrigerant in the A/C system based intercooler chiller on my twincharged Buick. -44 beats the hell out of -15. It'll fog the windows too in the summer. Lol.

The idea would be you would ultimately run the gasoline system lean and the heat in the air charge would do the vaporizing so you use it to provide the balance of your fuel. Freezing over would be my big concern but if you had enough heat I'd think it a non issue.
 
Trying to "flex" the map a bit makes a lot of sense. As a question what about building a tube with a nozzle on the end of it that has a 90 on it? Yeah I realize that disrupts air flow a bit but it may be worth it in the long run. Either that or some in car crazyness if you can stuff a rag in the inlet, drill/tap a hole and vacuum the shavings out. Would certainly not be the first time it's been done.

I also looked at doing that...but didn't have the confidence that I would get it even remotely centered or pointed the right way trying to drill and tap a straight hole in a curving aluminum pipe with a REALLY long flex shaft attached to a drill 90. This is essentially what I'm dealing with:

s-l1600.jpg


I had considered figuring out how to snake some 1/4" aluminum tubing down there are the proper angle and have the nozzle right by the compressor, but ultimately it's a pretty small ID and it would be a huge flow disruption. So I think the final solution is just to use an array of really fine garden misting nozzles. They make droplets a lot finer than typical alcohol injection nozzles. But are very low flow so it might take half a dozen of them in the airbox pointed at the turbo inlet. The air should be moving fast enough that for the most part the boundary layer should keep them from sticking to the wall as long as the droplets are fine enough. Supposedly below a certain micron droplet size they actually bounce off things and each other.

That's why I suggested the Motec first. Supposedly they have a huge amount of integration even shit like DBW.

The one (albeit untested) flaw of this idea is I believe you could end up dissolving the inert gas into the propane like CO2 into a soda which is typically done at 15ish PSI. That's why I was reluctant to work on something along those lines as I would be afraid it would cause a less than steady AFR as more inert gas absorbed into the LPG. Jetting shouldn't be bad with what's in the aftermarket I'd be looking for 150-200 PSI on the propane side just because that's likely where you'll end up on a hot day with a fullish tank. There are enough nitrous jets out there you should be able to figure something out.

Yeah, I haven't really looked into the motec. The only shop that I know of in the states that has done an aftermarket ECU on these uses a syvecs S12, which is a euro-manufactured aftermarket ECU of some kind that was specifically designed for integration and full control of V12 exotics. I mean the car has all sorts of wacky ionic current sensing in the spark plugs/ignition modules and a ridiculous amount of stuff that just won't work if the computer in that module isn't getting the right answers from the ECU, etc. The base price is like $10,000 plus you need a ton of accessories and someone with the knowledge to set it up and get everything working so the total cost really gets up there. I would never dream of doing that unless I won the damn lottery or something. Probably wouldn't even then, lol.

As far as the solubility of argon in propane or nitrous oxide...it's certainly something to think about and I had even tried to find information on that before, but it's kind of an obscure and weird search. Generally though, solubility is measured in like grams per kilogram. I can't imagine that fractions of a percent of mass worth of argon dissolved in the nitrous or propane is going to cause any measureable difference. Think about the weight of the contents of a bottle of argon gas vs the weight of the contents of liquid nitrous or propane in a bottle bottle. Some testing would tell, but I can't see it being a big deal.

The idea would be you would ultimately run the gasoline system lean and the heat in the air charge would do the vaporizing so you use it to provide the balance of your fuel. Freezing over would be my big concern but if you had enough heat I'd think it a non issue.

That's an interesting idea, but not plausible. The latent heat of vaporization of propane is 184 BTU/lb. Gasoline is around 150 BTU/lb. So you're only gaining like 22% cooling capacity even if you replace 100% of your fuel with propane. Does it get really cold? Yes. But the phase change cooling energy just isn't that great. To put it into perspective, water is pretty much the king at evaporative cooling energy at 970 BTU/lb.

Propane would offer you 61 degrees F of evaporative charge cooling at 12:1 AFR. if you replaced absolutely all of your fueling needs with it. Power level doesn't matter since it's a fixed ratio to airmass. Sounds ok until you compare it to gasoline which already gets you 50 degrees F of cooling energy. Compared to E85 or ethanol or methanol it's a trivial amount. Methanol will take 358 degrees F out of the charge. Obviously much of that is spent cooling other hot things in your intake tract since the air isn't that hot except on the wildest non-intercooled turbo setups. But the BTUs are there to do it.

If you were to use propane, it would take sacrificial propane vented to atmosphere to be able to spray enough to actively chill an intake charge a significant amount. And for that purpose, I would probably rather use CO2 anyway (probably cheaper, no fire hazard, colder boiling point, better latent heat of vaporization, etc.). Now with that, you *would* have to worry about freezing the moisture out of the air and blocking your core, lol. I used to have a propane bottle I would use to idle cars with dead fuel pumps into the shop. The line from the bottle would sure get frosty, but the intake manifolds would still be warm/hot if you had to drive it any distance at all.
 

Handsome Jesus

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I have pre-turbo on my car. I don't have a special nozzle holder or anything. I do believe there is a similar gain to be had on the inlet temperature, but the balance of injecting the proper amount of methanol would be something I would leave to dynamic simulation. I have been trying to get someone here at work to set up a basic Aspen simulation to determine the ideal amount of methanol per mass of air at a given temperature, with variables that could be manipulated, but haven't had the time to get that done yet.

I have found a small amount of blade tip erosion on the outer most tips of the compressor wheel (highest velocity) but nothing I care that much about. I think that your turn at the inlet theory of the methanol coalescing on the surface may be a bit exaggerated. That turbo is hot, all the time. it is right next to your exhaust manifold. Collection of methanol there would be pretty unlikely in my mind.

again the vaporization of the methanol will displace the air, so you don't get as much benefit, but you already accounted for that properly in your previous calculation (or what looks possible to me). I do like that methanol is a fuel though, versus something like CO2 which just takes up space in the cylinder and will not be burned.

I see a drop in IAT significantly throughout a dyno pull with the setup I am on right now (pre-turbo and post-intercooler) as to the improvement with and without pre-turbo, I don't currently have that data. I see an added benefit of higher intercooler efficiency with a lower discharge temperature going in.

anyway this comment is disjointed, but doesn't seem that out of place with everything else in here :iowtfrun2:
 
I have pre-turbo on my car. I don't have a special nozzle holder or anything. I do believe there is a similar gain to be had on the inlet temperature, but the balance of injecting the proper amount of methanol would be something I would leave to dynamic simulation. I have been trying to get someone here at work to set up a basic Aspen simulation to determine the ideal amount of methanol per mass of air at a given temperature, with variables that could be manipulated, but haven't had the time to get that done yet.

I have found a small amount of blade tip erosion on the outer most tips of the compressor wheel (highest velocity) but nothing I care that much about. I think that your turn at the inlet theory of the methanol coalescing on the surface may be a bit exaggerated. That turbo is hot, all the time. it is right next to your exhaust manifold. Collection of methanol there would be pretty unlikely in my mind.

again the vaporization of the methanol will displace the air, so you don't get as much benefit, but you already accounted for that properly in your previous calculation (or what looks possible to me). I do like that methanol is a fuel though, versus something like CO2 which just takes up space in the cylinder and will not be burned.

I see a drop in IAT significantly throughout a dyno pull with the setup I am on right now (pre-turbo and post-intercooler) as to the improvement with and without pre-turbo, I don't currently have that data. I see an added benefit of higher intercooler efficiency with a lower discharge temperature going in.

anyway this comment is disjointed, but doesn't seem that out of place with everything else in here :iowtfrun2:

Even if it evaporates on the inlet walls as opposed to forming droplets and working its way towards the turbo, that latent cooling effect then takes place on the housing, not the air stream, but the volumetric displacement is still the same so mass flow through the turbo might actually be lower overall. That's essentially what happened in that EPA study I posted. The charge was either re-heated by intake piping, or some of the spray evaporated to cool the walls as opposed to the charge air resulting in lower air mass flow through the engine.

I think it is definitely possible to achieve some additional benefits, but it would also be easy (in fact almost guaranteed) to actually reduce mass air flow as a result of the expansion/air displacement. I'm convinced injecting as close to the actual compressor wheel as possible is the way to go for increasing mass flow through the turbo, and injecting as close to the intake valve as possible for increasing mass air flow through the engine itself. Backed up by the EPA link a few posts back.
 
I see a drop in IAT significantly throughout a dyno pull with the setup I am on right now (pre-turbo and post-intercooler) as to the improvement with and without pre-turbo, I don't currently have that data. I see an added benefit of higher intercooler efficiency with a lower discharge temperature going in.

That would probably be a lower efficiency, actually. Any time you have lower temperature differential across a heat exchanger (between the charge air and ambient...or charge air and your intercooler water) you are going to get less efficiency out of it. So with a lower inlet temperature, while you may still end up with lower outlet temps it's because the intercooler is doing less work not because it is more efficient. In fact, it will definitely be less efficient in cooling humid air...the latent heat of vaporization works in both directions. It takes a tremendous amount more energy to cool humid air than it does dry air. The good news is you aren't going to condense out ALL the water that you vaporize because the air wasn't saturated to start with and you're also still talking about temperatures higher than ambient as well. So there is definitely still some net cooling (as evidenced by your lower outlet temps).
 
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