(Race Car) Injecting Gasoline Pre-Turbo and No Intercooler

[CTX-SLPR]

***Race Car Only, not a street car***

So my LSR motor is coming out of storage and I'll start messing with it again sometime soon. Since I've had time to think but not do anything an idea struck me. Can I spray fuel pre-turbo and get away with no intercooler? This would significantly simplify my build as I'd not have to worry about plumbing an Air-to-Water, mounting it, and associated hang ups. Idea would be to have part of my mechanical injectors spraying pre-turbo then have 6 port mechanical injectors, 1 in each runner. The injectors are not large so I have 10 of them in total.

Based on readings, the carbon seals on turbos are needed for those that are between the throttle blades and the engine due to the vacuum pulled on the bearings. Since the turbo will still be upstream of the throttle in this case, I don't think I'd need any special turbo.

Thoughts and Thanks

 

[charlief1]

Did a bunch of research on carb turbo set up and earlier designs. If you inject pre turbo you meed to make sure it's a fine mist and at least 12" before the turbo so it will atomize properly. Look up some of the stuff Smokey Yunik did in the 80's as well as ENG-TIPS forum for more info.

 

[TurboTnZ06]

Instead of gas, why not spray pure meth pre-turbo? It's outlawed in the heads up turbo size specific classes because it makes the smaller turbo act like a bigger turbo...

 

[CTX-SLPR]

Methanol is not class legal in Gas classes and I need all 10 injectors (repurposed Bosch k-jet). I could put the 4 "common" injectors in the inlet ahead of the turbo, post turbo, or post throttle body. Pre-turbo or post turbo just seem like they could take the place of the intercooler and save some complexity.

 

[ijames]

This is all theoretical, but I think you will have a lot of problems with puddling and fuel delivery at idle and part throttle unless you only inject pre-turbo at wot, and now you will have wet flow through the throttle body and plenum so you might have fuel distribution issues at wot. Also, you will have a flammable mixture in a much larger volume than just the runners or manifold plenum so a backfire is going to be bad. As for cooling, you know the hp you plan to make and the approximate afr, so you can calculate the fuel and air mass per second. Then calculate the heat of evaporation of 40% of your fuel and see how much that will cool down that mass of air, using some reasonable turbo efficiency to estimate the post turbo air temperature without evaporative cooling. Being a mere (lazy) chemist, I'm going to let the physicist run the numbers .

Back in the 90's I heard a couple of anecdotal stories about erosion and damage to the compressor wheel from guys spraying water injection directly into the turbo on some non-Buicks. This was on street cars, the water was much more a stream than mist since their thought was to let the turbo do the atomization, and I really don't know how many miles were involved but it has to have been a lot more than your car will see.

 

[CTX-SLPR]

So I did the math best I can with only a phone internet connection to look up constants and have come to the conclusion that based on my high pressure ratio (2.92), and a modest 82% turbo efficiency, the gas spray can only get me 39℉ in boiling and then vaporizing ~1lb/min of fuel. Water spray on top of that still takes 1/3 the fuel volume in water to get to ~120℉ outlet temp. Sounds like injecting post throttle body makes the most sense as does an intercooler.
1 Liter a minute of water sounds like I'd be drowning the motor. However messing with the turbo sizing by bringing the density of the flow through the turbo up with some water injection does have an attraction.

Charlie, rummaged around on ENG-TIPS and couldn't find much. Any direct references?

 

[charlief1]

Charlie, rummaged around on ENG-TIPS and couldn't find much. Any direct references?

I had to do a bunch of reading in the auto and aeronautics section to find the info. Don't allow the search limits but expand them some. When I was going over there on a regular basis I had to go way back to find the info I was looking for.

 

[turbofabricator]

Back in 1985 I crewed on an Unlimited Hydroplane team building Rolls Royce Griffons. The engines came with a liquid to air after cooler (after the two 14" centrifugal compressors) We removed the after cooler because when racing in salt water if there was a back fire it would rupture the core and then leak salt water into the intake. (Bad deal) we upped the water/alcohol to compensate. We went through 65 gallons of 115/145 AV gas with an addative, 150 lbs of Nitrous, 2-4 gallons of oil, and 25 GALLONS of water/methanol. We sprayed it into the supercharger inlet. Never had an issue with compressor erosion.
With that said, injecting fuel into a turbo can create a "possible" safety issue. If the engine backfires, it could create a very hazardous situation. If you can run water injection, do it. I ran water injection on my Buick with no intercooler back in 1989. Worked well.

 

[nonosv6]

The infamous Bruce rest in peace did some research on this back in early to mid 2000s. I know he was running no intercooler and had injectors in the up pipe I believe. I think his documentation is somewhere on this site but def on gnttype.org .. If I have some time ill try to look it up

 

[nonosv6]

so I did some quick searching and, I cant find the articles I was looking for. Bruce Plecan is his name. I know he was working on something with eliminating the intercooler either using alky injection and or 7th injectors or something. I know , not very helpful but there is info floating around in here somewhere....Joel

 

[jimmymorrisonjr]

I am not a pro by any means so take what I write as just thoughts and not fact please. All liquids have a latent heat of evaporation that varies with temperature. Alcohol works very well with no intercooler since the latent heat of evaporation is more than 2 times that of gasoline and you need almost twice as much to burn. You effectively have four times more cooling with alcohol than gasoline.
Knowing you can not use alcohol you would like to cool the charge with gas. I think this is an ill fated course. If you heat and evaporate the gas early in the intake charge you will not be able to take advantage of it's cooling benifits in the cylinder where you need it more.
As said, water does work as it has a latent heat of evaporation value much higher than alcohol. I don't know anything more than that has been done.

 

[CTX-SLPR]

so I did some quick searching and, I cant find the articles I was looking for. Bruce Plecan is his name. I know he was working on something with eliminating the intercooler either using alky injection and or 7th injectors or something. I know , not very helpful but there is info floating around in here somewhere....Joel

Bruce and I actually hung out while I was stationed in Dayton, OH. I'm familiar with the experiment and he did have decent luck with it (if I remember it correctly the major selling point was the near instant recovery from being on boost). It would be nice to find it.

I am not a pro by any means so take what I write as just thoughts and not fact please. All liquids have a latent heat of evaporation that varies with temperature. Alcohol works very well with no intercooler since the latent heat of evaporation is more than 2 times that of gasoline and you need almost twice as much to burn. You effectively have four times more cooling with alcohol than gasoline.
Knowing you can not use alcohol you would like to cool the charge with gas. I think this is an ill fated course. If you heat and evaporate the gas early in the intake charge you will not be able to take advantage of it's cooling benifits in the cylinder where you need it more.
As said, water does work as it has a latent heat of evaporation value much higher than alcohol. I don't know anything more than that has been done.

The big impact I can see so far is messing with the turbo map by changing the mass flow rate with added water. Beyond that, at this point it's mainly so I can go from Gas (regulated event fuel) to Fuel (anything you want) by just dumping some alky in the water tank or the like.