FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: AlanCasida on June 30, 2016, 08:55:58 PM
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I have been mulling over putting a 6-871 supercharger on the 452(yes, FE !!) that is going in my 65 Mustang. My motor currently has a static comp of around 9 to 1 using Aries dished pistons and OEM MR heads. I would want to use one to make power, not just to look cool. Is that too much to run on pump gas. I wouldn't want to underdrive it a bunch as I feel that kind of defeats the purpose on having one. Thanks; guys.
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N/M
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I think 9:1 is too high for pump gas and any significant amount of boost. A Roots type supercharger adds a lot of heat to the intake charge, which will make it more detonation prone, and with that CR I think you'd be asking for trouble with pump gas. I'd be looking at 8:1 if you want to run 8+ pounds of boost on pump gas. My centrifugally supercharged FE ran 8.5:1, 15-17 pounds of boost, a good ignition retard when the boost came up, and it still needed 110 at the track.
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Jay is right. 8.0:1 is about the max you can run if you want to push 6-8 lbs of boost with a positive displacement blower.
Here's a chart that gives a really rough estimate of equivalent static compression for boost and engine compression ratio:
(http://i905.photobucket.com/albums/ac255/ottodyn/6-30-2016%2010-23-22%20PM_zps46nx7lrk.png)
From this article:
http://www.jegs.com/tech-articles/superchargers.html
Screw-type Eaton blowers are a bit more efficient and can tolerate slightly more engine C/R, but the above info gets you in the ballpark.
- Bill
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Wow, that really puts it into perspective when some of these guys are pushing 25-30+ lbs of boost on turbo engines. Granted, they're intercooled, but still...
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Don't overlook the possibilities inherent in 'chemical intercooling'. Setting up a system that uses a Hobbs switch to turn on a methanol spray as the boost comes up will do wonders. I have successfully run 11 to 1 and 20+ pounds of boost with such a system. A boost-referenced regulator and a pump capable of putting out enough more than the boost pressure are both necessary.
KS
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What if you ran it on E85 only? The alcohol has a cooling effect besides the race gas level octane. Never really seen that discussed with regard to a Roots boost.
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E85 works well in any boosted application, for various reasons. 1, E85 has a colder burn so the cylinder doesn't get as hot. 2, E85 has a broad lambda range of roughly 0.71 to 0.87, or in AFR, about 7.0:1 all the way to 8.5:1. When E85 has a stoich at 9.77:1, that's saying a lot about the effective range you can run it at. 3, You're also running ~30% more fuel than compared to gasoline or gasohol, so you're going to be able to cool down the cylinder a lot better through heat transfer from the cylinder to the fuel. 4, E85 has a higher resistance to detonation that allows for more flexibility in compression. The only real downside to E85 is that you have to use more fuel as a result of the stoich AFR. For an engine built to go fast though, it's a decent option and cheaper than running methanol.
If you want to run E85 though, it's best to design the engine to ONLY run on E85. This is where flex fuel vehicles suck, in order to run both E85 and regular gas, the engine has to be a compromise between the two. So, I'd recommend choosing a specific fuel to run and stick to that fuel if you really want to get the most out of that fuel. E85 sucks for naturally aspired vehicles, you can't really extract the potential out of the fuel to make up for the increased consumption in fuel. Unless maybe you used like a 14:1 CR and didn't run a cam with a high ICA that would bleed off the pressure. Which would destroy an engine running typical pump gas.
Since we're talking about fuel and FE's, does anyone know if it's ever been tried to create a diesel FE? Maybe that could be Jay's next SOHC project.... imagine the torque....
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So based on the chart Bill Conley posted on E85 you could run 8 plus pounds of boost at 9 to 1 static. Don't know how available it is to everyone but here in West Michigan they brew it locally. Next next FE to run will be E85 only.
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I don't know the exact recommended max static CR for E85. Also, your static CR isn't all that important. What is really important to pay attention to is your dynamic compression ratio. You could have a really high static CR and use an aggressive cam with a late intake closing angle to bleed off the pressure to prevent detonation. You only start building pressure once all the valves are closed. I would look at this from a dynamic compression ratio and dynamic cylinder pressure point of view. Get some feedback on what cylinder pressures people have been able to hit with E85, besides what CR they have run. Also remember that boost is addicting. It's probably better to just stick with a low CR setup and just crank up the boost. It's easy to turn down (or up) the boost once you know how the engine will behave. It's a lot harder to change the static compression ratio.
If you were building a NA engine, your choices that impact the static CR would be far more important. With FI, it's probably better to stay low and compensate later. If any of our wise men disagree with this, please correct me.
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Hi I am building a injected 8/71 427 Cammer with a 4 1/8 crank my altitude is between 4 to 6 thousand feet so that should make a difference as far close to 9 , and the E85 stuff I know nothing about can you get it anywhere or is it hard to find it sounds kinda cool. Leny Mason
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Leny, it depends on your area. Some places E85 is at most gas stations. Other areas, it hardly exists.
http://www.ethanolretailer.com/flex-fuel-station-finder
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Hi Autoholic It looks like Great falls Mt is the closest place to buy it , 100 miles away do you think the altitude makes and difference . Leny Mason
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Altitude always makes a difference on an internal combustion engine. The density of the air will dictate how much boost you put into a setup. The good thing about forced induction is that you can compensate for the density of the air at higher altitude. That's all a supercharger or turbo does, it increases the density of the air. If you use the ideal gas law, PV=nRT. n and R are constants, the only thing that changes will be pressure, volume and temperature. Consider volume constant in this case, and you're left with pressure and temperature. The initial pressure is that of the atmosphere where you are, and the same for temp. The final pressure will be atmosphere plus whatever your boost pressure is. You solve for temp, that will be the intake air temp the engine sees. Naturally, the lower in elevation you are, the less work the supercharger will have to do to reach the same pressure, lowering your IAT's. The more you compress air, the hotter that air will be. With an old school blower, you don't have an intercooler so you'd have to inject something cold to bring down temps, be that methanol, water or nitrous. You could theoretically create a custom blower plenum that has an intercooler, not sure if it has ever been done for the FE.
If the temp is 75 *F outside, at sea level atmospheric pressure is 14.7 psi, 4000 ft the atmospheric pressure is ~12.75 psi and at 6000 ft atmospheric pressure is ~11.86 psi. So in order to compensate for elevation at 4000 ft, the boost would have to increase ~1.95 psi and at 6000 ft, the boost would have to increase ~2.84 psi. When you consider the fact that you monitor boost pressure by at least 1 psi if not smaller, that is important. At 4000 ft, you've lost 13% of your initial pressure and at 6000 ft, 19%. The temperature outside plays a huge role as well, the colder it is the more dense your air will be as well as having colder IAT's.
I should note that I haven't discussed how the fuel will impact all this. The more fuel you inject, the colder the incoming charge will be. If you were to try and create an intercooler for an old school blower setup, you'd be restricted to either mechanical or electrical fuel injection at the individual runners. The intercooler would trap too much fuel, which would be dangerous besides making it hard to tune.
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The guy that is helping me set this up thinks that 9 would be better so when cruising and the throttle plate is only open a bit I will have better power when going up our mountain passes when the blower is not working hard. Thanks for your input. the 85 fuel may be hard to find here I would not mind using it. Leny Mason
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I second the motion for methanol/water injection. I raced for years with 9.8 : 1 compression under 15psi boost, but with a 50/50 blend of water / methanol I never had a problem using 93 octane. And, I ran a full 38 degrees ignition advance. Check out Snow Performance. Without a methanol kit, you're not getting anywhere near the full power potential of your boost.
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A blown 427 SOHC will not have problems making power down low. I bet your engine will make more power at 2000 rpm's than some of the new cars being sold today.
Leny, good luck and share some pictures of your build. I'm very interested in seeing a new blown SOHC being built. If you haven't found all the parts you need for your build, you might want to try and get a hold of Paul Munro. He's in Australia and he casts various parts for the SOHC, including new blower plenums. What vehicle are you looking to drop such a beauty into? If you don't plan on driving it all that often, you could just buy E85 or even E100 from a company like VP Racing or Rocket Fuel. Or just go straight to methanol.
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You said it yourself: " I would want to use one to make power, not just to look cool."
IF you want a serious blown/power adder motor.That adder dictates pretty much everything going in/on that motor is selected with that power adder in mind
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I built my 8-71 blown 452FE to look cool...and accidentally ended up making stupid power!:)
I chose an 8-71 over a 6-71 simply because you can turn it a little slower (making less heat) for the same boost. And, of course, it looks bigger too.
The best way for me to describe driving the same car normally aspirated vs. boosted is that now it pulls as hard in high gear as it did in second before. Crazy!
My car has 8.5:1 CP blower pistons. I have easy access to 100LL Avgas at $5 a gallon so I keep it handy. I also have a Snow water/meth system on it that starts injecting at 4lbs. and is fully "on" a 9lbs. I'm fairly confidant I could go with 91 octane California "moonshine" gas and water/meth, but I don't because I don't have to.
My car seems to like a fairly aggressive advance curve to run cooler around town but my Electromotive distributorless ignition has a linear programable retard feature. I give it 18 initial, 34 total by 3000rpm, then start pulling 2* per 1000rpm after that. Shift at 6K.
The Snow water/meth kit is a pretty easy install with the injectors in aluminum plates under the carbs. My pump and tank are in the trunk. I use the Snow "Boost Juice" from Summit $35 for 4 one gallon jugs, but you could mix your own distilled water and methanol for cheaper. The controller is kind'a tricky to get right...but seems to stay put once you dial it in.
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Hi If I can figure out how to put some pictures on this sight I will, it is a 1964 Comet We are making a full frame for it now four link my rear tires are 17x33x16 on the rear I was going to straight axle it but I changed my mind now is the time to change it to a Mustang two, We made the front fenders six inches longer along with the wheelbase, that made a lot more room in the engine bay for all the blower drive and distributor I am making a 90* gear box for the distributor to get out of the way of the blower belt it started out as a nice one owner car. Leny Mason
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What exactly are you doing for the distributor? I believe the blown SOHC's used a distributor from a Ford flathead and then ran it off of the long timing chain, using the fuel pump gear. Maybe our members who know more about the blown SOHC's will chime in on how it was done.
I can't find any pictures of a blown SOHC that did this way, but the Suncammer I think did it this way.
(http://www.stevecookcreations.com/images/gallery-picture/ricks-5.jpg)
(http://www.stevecookcreations.com/images/gallery-picture/ricks-2.jpg)
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Depends on your ability to control your timing, afr, and octane. Essentially the big deal with "boost" is controlling cylinder pressure and "octane". when dealing with factory engines and 9+ to 11:1 static compression ratio when adding boost the knock sensor is happy when dialing back the timing under high pressure conditions aka high load(lower rpm and high boost/throttle angle). Using water/meth has shown that you can get away with alot more timing with pump gas. Favor meth further away from the combustion chamber and then favor water closer to the chamber. Water can soak up alot of chamber / egt temp supposedly. When Running enough water/meth there isn't a a big difference between 87 and 91 pump as far as the knock sensor is concerned.
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Wow I have not seen that Car before the water pump is interesting, any way that distributor is the same one I have with blower belt on I only have about one quarter inch and that is a stretch, so I am using the Jim Bairillo's front cover that came with the Rotor Phase distributor then I found a 90* gear box 1 to 1 so I can get it out of the way, I will try to do some pictures . Leny Mason
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Thanks for all the input, guys. You are the best! Sounds kind of like I figured, I'll really need to plan on at least pistons for this.
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I have easy access to 100LL Avgas at $5 a gallon so I keep it handy.
I'm a little jealous, Tommy. 110LL here in Ohio is almost $8 a gallon, and that's within 3 miles of a refinery. Seems odd considering gas is cheaper here, I think.
Does anyone know the longer term effects of running water through an engine? I know it turns to steam, but it seems that there would be some moisture left behind that would have to condense, and I'm curious how that would affect aluminum heads, cylinder bores, valve seating and rings.
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N/M
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Thanks for everyone's input!
Here is a bit of information I got off of Blower Drive Service in their FAQ
The question asked was "What type of pistons and compression should I be running on my blower"
Their answer:In the last decade as the octane rating of gasoline decreases and the demand for more horsepower increase, there is more of a possibility for detonation. Forged piston made for blown systems are highly recommended. Also using 8.5 to 9.1 compression ratio and less blower boost will keep the engine cooler. When you run a lower compression engine and raise the boost levels, this elevates the temperature of the air charge to your engine, requiring you to buy higher octane gasoline to suppress detonation.
I am right at 9.0 now. If I run a slightly thicker head gasket or have the combustion chamber opened up a little on the heads I think I'd be right where I need to be. I have a bare pair of Edelbrock 76cc heads laying around. My machine shop has a service of opening them up to 88cc(stock MR). I'd have to check against a head gasket and of course talk with them but I might be able to open them up to maybe a 95cc or so and get down to about 8.5.
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Alan, I would not increase the combustion chamber to get the lower compression. Those heads are not the thickest of metal, and cutting them that much takes the temper out of the heat treatment. It is much more wise to buy the proper pistons for the desired compression ratio and still have a useable set of heads for another build. JMO, but 8.5:1 is safe, and a FE has enough torque to still be able to get out of its own way on the street. My engine was built with ~8.7:1, and I ran 14 PSI on the street with boost timing retard. Joe-JDC