TorqStorm Supercharger build advice needed

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Well as our buddy @TT5.9mag argues and correctly, there's more than one school of thought. None of them are necessarily right or wrong, just different. My experience is with roots type blowers such as 471, 671, and 871 and the small B&M roots blowers like the 144. I've built several and they seemed to respond better with lower compression. That doesn't mean higher compression cannot work, but it can mean you have less "wiggle room" for detonation. Everything has to be perfect. As you say, I think you're about right with your projected effective compression ratio with around 12:1 with the blower on a 9:1 engine.

Now this part is my personal opinion and the WHY of why I do not like to run much higher than about a flat 8:1 on a blown engine. All of these timing retards pull timing out based on boost. What happens to an engine when you pull timing out? The power drops off. That kinda defeats the purpose of a blower, doesn't it? A lower compression engine will pull much less timing out. In fact, On the 144 blower engine we built, we didn't even have a boost retard on that engine and ran about 7 PSI. That engine was blueprinted "somewhere" under 8:1. I don't remember the exact specs, as this was probably about 1985 or 1986. This was with a small block Chevy (stock stroke 350) and in fact at B&M's suggestion that we did not need a boost retard if we ran the engine on premium. That's what we did and never had detonation. We used closed chamber 350HP heads and a dished piston we got to zero deck, so there was a small amount of quench with the about 1/2" wide ring around the outside of the piston that saw zero deck height, so it worked.

I'm not advising that you throw the boost retard in the ditch. Just tellin what worked for us. We did have boost retard on the others, although only pulling a small amount of timing. I've just never been a proponent of pulling timing out of an engine, nor water injection. What's water to to a fire? LOL I guess it's the old man in me. lol Technology has come light years ahead of where we were back then. So I would certainly take advantage of it and will when and if I build a blown slant.....and I'm probably going to at some point before I kick off.

But I want something stickin through the driver's side of the hood. lol
 
There is a big difference in the boost pressure, and CR relationship, for "positive drive" superchargers and turbochargers. Also between street drivers which spend 90 % of their time at less the full throttle, and race cars which spend most of their time at full throttle. Boats are another thing. They are usually operated at a "steady" throttle. A turbo in a street car (personal opinion) should have more CR and less boost than a race car. A turbo generally doesn't produce much boost at low rpm steady throttle conditions. It should therefore have more CR to get the car moving away from stop signs, before the boost takes over. A positive drive super charger generally has the same amount of boost available at the same rpm, regardless of throttle position, or load. So I would think you would want less CR, and more boost. (As I previously stated, I have no hands on with super chargers)
 
I tend to agree with both of the above comments in general. @RustyRatRod i will say this, don’t think of it as pulling timing out, think of it as needing a new optimal timing number. As the air in the chamber is now much more dense, the optimal timing number will drop from an optimal NA number. NA an engine might like 34-35 degrees for wot. That same engine on boost might make the best power on 28-30 degrees. For example;
My 489 BBC on the dyno NA made best power at 39 degrees. Same engine only with turbos made best power at 30 degrees at 9psi. We swung the timing all over and were NOT octane limited. We ran 118 octane for initial testing. The new dense fuel mixture “required” a new timing number.
One more point, dropping compression on a boosted engine has the exact same effect as dropping the compression on an NA engine. Boost is a multiplier.
 
TT5.9mag said:
I tend to agree with both of the above comments in general. @RustyRatRod i will say this, don’t think of it as pulling timing out, think of it as needing a new optimal timing number. As the air in the chamber is now much more dense, the optimal timing number will drop from an optimal NA number. NA an engine might like 34-35 degrees for wot. That same engine on boost might make the best power on 28-30 degrees. For example;
My 489 BBC on the dyno NA made best power at 39 degrees. Same engine only with turbos made best power at 30 degrees at 9psi. We swung the timing all over and were NOT octane limited. We ran 118 octane for initial testing. The new dense fuel mixture “required” a new timing number.
One more point, dropping compression on a boosted engine has the exact same effect as dropping the compression on an NA engine. Boost is a multiplier.
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I'll go along with that. Akin to needing less timing with higher cylinder pressure in a N/A engine.
 
In a recent engine masters episode “the turbo mo ho 440” Steve said the engine was so lame (speaking about compression and cylinder pressure) that he didn’t have to pull timing at all to run it on boost. It’s worth a watch.
 
Let's not forget this boosted six is pushing a W-series truck, the heat-load is going to be higher than an a-body, I honestly wouldn't do this w/o forged slugs. The cooling system should also be the best available, which should be easy for a truck app.
Although I hate E85 for NA use, I'd seriously consider it for boosted apps, especially this one. Obviously alcohol compatible component selection & moisture control needs to be considered.
 
Thanks guys. This is the type of stuff I was hoping to hear. Any thoughts on my ring gap comment?
 
Killer6 said:
, I honestly wouldn't do this w/o forged slugs.
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I don't agree. If the tune up is good, and no detonation, cast pistons will be fine. If into detonation either type piston will fail. In my first turbo motor I had forged pistons and broke some (detonation) 11-12 lbs boost. My recent nitrous motors I use mostly stock cast pistons. Have run as high as 225 hp shot fogger on a 170 slant. Mostly good, sometimes not so good. Proper tune up is the key.
 
Charrlie_S said:
I don't agree. If the tune up is good, and no detonation, cast pistons will be fine. If into detonation either type piston will fail. In my first turbo motor I had forged pistons and broke some (detonation) 11-12 lbs boost. My recent nitrous motors I use mostly stock cast pistons. Have run as high as 225 hp shot fogger on a 170 slant. Mostly good, sometimes not so good. Proper tune up is the key.
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The key to no failure with any piston, IMO, is NOT running lean.
 
Jerry Miller said:
Thanks guys. This is the type of stuff I was hoping to hear. Any thoughts on my ring gap comment?
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.0065-.007 times bore size will give you ring gap for boost.
It will run absolutely fine there NA before the blower goes on. You will not have significantly more blowby NA than an NA gapped ring. As long as they’re seated and oriented on the piston properly.
 
Killer6 said:
Let's not forget this boosted six is pushing a W-series truck, the heat-load is going to be higher than an a-body, I honestly wouldn't do this w/o forged slugs. The cooling system should also be the best available, which should be easy for a truck app.
Although I hate E85 for NA use, I'd seriously consider it for boosted apps, especially this one. Obviously alcohol compatible component selection & moisture control needs to be considered.
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All good points and things to think about. One caveat though. This will likely be a 200-230 hp engine on 6-8 psi. Heat is directly related to hp and load. He will be heavy with big tires but he does have steep gears. I think it could be done on a stock replacement type piston and 91 octane. Once again carefull tuning will be key.
 
I'm 8.5-9ish to one on crap 91 ( I do have an intercooler to help with intake temps ). very conservative with my tune. Have been sneaking up on it ( 6psi is a Lot of fun already ).
 
TT5.9mag said:
.0065-.007 times bore size will give you ring gap for boost.
It will run absolutely fine there NA before the blower goes on. You will not have significantly more blowby NA than an NA gapped ring. As long as they’re seated and oriented on the piston properly.
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Naw. I always gap rings wide even on N/A engines. It's just good insurance, especially here in the south where it gets so danged HOT and engines really go through it in the summer.
 
You guys SUCK. I shouldn't have ever even pend this thread. Now I'm really thinking about a boosted engine. lol Maybe next build.
 
TT5.9mag said:
All good points and things to think about. One caveat though. This will likely be a 200-230 hp engine on 6-8 psi. Heat is directly related to hp and load. He will be heavy with big tires but he does have steep gears. I think it could be done on a stock replacement type piston and 91 octane. Once again carefull tuning will be key.
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Here's you a curve ball. What about this? Use manifold vacuum on the vacuum advance for the boost retard. Set timing with the vacuum can attached. That way, when vacuum drops off........OR when boost is present, timing falls off some. Cheap man's boost retard......but would it work?
 
RustyRatRod said:
Here's you a curve ball. What about this? Use manifold vacuum on the vacuum advance for the boost retard. Set timing with the vacuum can attached. That way, when vacuum drops off........OR when boost is present, timing falls off some. Cheap man's boost retard......but would it work?
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This has been done and does work. Kind of. I think it was Volvo or maybe Volkswagen that had a vacuum advance AND boost retard distributor. But with the amount of people that barely understand how mechanical advance and vacuum advance actually work (let alone tune them), an MSD box and a dial on the dash is much safer and easier to make right.
 
TT5.9mag said:
This has been done and does work. Kind of. I think it was Volvo or maybe Volkswagen that had a vacuum advance AND boost retard distributor. But with the amount of people that barely understand how mechanical advance and vacuum advance actually work (let alone tune them), an MSD box and a dial on the dash is much safer and easier to make right.
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Probably, but WE could do it I bet. I would want to find an adjustable vacuum advance that had the highest amount of advance I could find. That would give a lot of adjustment. It would certainly be interesting to try.
 
TT5.9mag said:
This has been done and does work. Kind of. I think it was Volvo or maybe Volkswagen that had a vacuum advance AND boost retard distributor.
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Corvair.
My original turbo car, back in 1979-80 used a modified Corvair turbo. I tried using the distributer vacuum advance hooked up to manifold vacuum, and adjusted the curve accordingly. It wasn't very good. Wound up using a MSD "ping control". Better, but not as good as a "boost timing master" (which wasn't on the market then). Also did not have AFM meters back then. Tuning was a *****. None of the turbo companies would give out any info either. Propriety info, don't you know? Broke some parts but kept learning and improving. Was able to drive to the track put on the slicks and run lower 13's at about 104 mph. 170 engine, about 2800-2900 lbs
PS: Still have that car and engine. Engine is out for freshening up.
 
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RustyRatRod said:
Probably, but WE could do it I bet. I would want to find an adjustable vacuum advance that had the highest amount of advance I could find. That would give a lot of adjustment. It would certainly be interesting to try.
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I have no doubt you can make something like that work. But you’d be doing it just to do it. The aftermarket in the last few years has exploded with really good stuff to make this type of thing simple. I’ve blown up too much junk already and am at the point of just pushing the easy button. I’d like to follow along if you do try it though.
 
RustyRatRod said:
You guys SUCK. I shouldn't have ever even pend this thread. Now I'm really thinking about a boosted engine. lol Maybe next build.
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Ha ha! Don’t do it. You’ll never want an NA engine again. I certainly don’t.
 
TT5.9mag said:
I have no doubt you can make something like that work. But you’d be doing it just to do it. The aftermarket in the last few years has exploded with really good stuff to make this type of thing simple. I’ve blown up too much junk already and am at the point of just pushing the easy button. I’d like to follow along if you do try it though.
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No, I'd be doin it to save 700 bucks. LMAO.
 
TT5.9mag said:
Ha ha! Don’t do it. You’ll never want an NA engine again. I certainly don’t.
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I don't see how I could ever afford it. Besides, I'm pretty happy with what I have.
 
Thanks again. This is great info. I like the thought about using the vacuum advance idea. I had wondered if any one had ever set an advance up in reverse to use a boost reference and then I saw that comment. I used to be a big diesel nut with the first Ford 7.3 PowerStrokes. We did all sorts of out of the box stuff, especially when the aftermarket support wasn’t quite there yet.
 
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