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I was just watching that Horsepower TV show.......You know the one, everything is chrome.
Anyways, they bolted a blower on a BB Chevy in a 69 Chevelle. On top of that there is a spacer with 8 fuel injectors in it and an injector scoop on top of that.

Now, I don't pretend to know very much about blowers or fuel injection for that matter, but I always thought that fuel injection, especially 8 fuel injectors should run into the engine as close to the cylinders as possible. What's the point of having 8 injectors on top of a blower? By the time it runs through the blower to the cylinders......you might as well just have one big throttle body on top of that blower. Am I wrong here? Can someone explain to me the purpose of those 8 injectors, if not just for looks?
 

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Didn't see the show and didn't even know it was still on, but, installing the injectors in that location is just another hybrid varient of a throttle body concept. Would be easier to dial down the pluse width in high HP applications with 8 injectors. Not uncommon at all.
 

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If I'm not mistaken they had 16 80 lb. injectors in that plate. Not all that uncommon to run injectors above the blower since the fuel cools the rotors. I also think they were running batch fire on the injectors. There would be no reason to run sequential with that setup and batch fire (or bank fire) is the easiest to control since it fires all the injectors on one side at a time. At least that's the way I understand it. Just think of is as a fancy TBI setup. They gained over 300 hp with that setup over a Demon carb and air gap manifold. Pretty impressive.
 

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EFI Rules and Carbs Drool
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poncho62,

Just another example of people (BDS or any other manufacturer) not thinking outside the box. I'd be willing to bet they never even gave multiport a second thought and it was more a matter of convenience and packaging. This way they just slap a fuel block and bugcatcher on and don't have to worry about dozens of different manifolds and fuel rails, etc for different applications. Just because they do it that way doesn't mean there aren't better ways to do it.

There seems to be two totally opposing groups concerning the application of fuel injection on blown motors. Some have the opinion that the injectors must be installed above the blower for cooling purposes (ala BDS). I suppose there could be some truth to that, but I talked to others that disagree.

Look at countless mutiport EFI engines that have blowers. Spend some time on some modular Mustang forums and you'll find those guys get crazy horsepower from those setups. BUT, the blowers are a different configuration and are much more efficient than the roots design, but when you compress air, you still generate heat.

It's my opinion that the yes the fuel has a cooling effect, but the same amount of heat is generated by compressing the air regardless of where the fuel is injected. Obviously, the higher the boost, the more heat is generated. What I don't know is the effect heat has on the rotating parts. A competition blower with very close tolerances my be in danger of damaging the rotors when it gets hot (over 250 degrees), but the case should also expand at the same rate to eliminate interference. I also think having the injectors down by the intake valves on a muliport system is a more effective way of cooling the intake charge. (Your not loosing that cooling effect to the blower and intake plenum)

I do know the Ford GT with the 550 HP engine has a water to air intercooler from the factory mounted under the blower.

I know of a couple people building blown multiport engines using a roots type blower, so we'll just have to wait and see as more people experiment with this.
 

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there are valid points here. but i have to disagree with you all, to a point. i think it is because, to place the injectors in the intake manifold. the blower would have to be raised up at least 4". this would cause it to look funny to some people(me being one). and it would cause hood clearance issues with some cars/trucks. causing lost sales.


+ that plate system looks pretty darn good. i would be proud to roll that.
just my .02
 

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bentwings
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Having been around blowers and FI for a long time both race and street let me add a few words.

First the 6-71 or any of the "71 blowers do need some cooling. You can use the fuel alcohol is best, gas, or nitro. Most of the race stuff uses hat nozzels and ports. The hats work at idle and part throttle and the ports come on at full throttle. Basically. It's more complicated than that but sufficient for here. If you don't have the cooling and you get some big heat either from boost and or motor heat you will score the rotors and case and blow a bunch of aluminum shavings into the motor.

I think we are refering to a street application so it would be nice to have the same thing with and EFI. Maybe run 4 of 8 hat nozzles part time and all of the ports all the time for even mixture. However practicality and cost enter in here. You can put all the fuel in the hat and make some minor fuel distribution corrections by moving the blower slightly and eliminate the ports. Again reality sets in.....it's not a racer, every last hp is not required and it costs a lot to experiment. The averge location works very well and produces one pile of hp when desired. The fuel distribution and atomization is pretty good. EFI done right makes it so the blower never backfires which can instantly ruin a good blower. Injector capacity is available for what ever you need.

It takes a spacer to run EFI in the hat and Vortec is right it would take an even larger bottom spacer to run ports. You would probably add 6 inches to the height of the system. Besides looking strange (to my eye) it would be hard to live with on the street. EFI is a $4000 plus option after the $3200 for the blower system so it is not in every ones budget.

You can run 5-6 psi boost and get more hp than you will ever need on the street. Honest, try making a dozen full throttle 200 yd tune up runs with 600+ hp somewhere on the street and not attracting a black and white or a maroon and gold or what ever your local LEO's drive.

There is case for the smaller blowers like what is run on the T-Bird SC. I had one for 200k miles. It ran like a charm and made a lot of power for a 3.8 L motor and got 25+ mpg. It had an EFI and injected the fuel right in the ports. None in the blower. It also had 14psi boost. However the blower was much smaller so it could run tighter clearances and run considerably faster overdrive. It also had an intercooler.

As for the clearances in the blower. The 6-71 or other-71 blowers for street are relatively loose by race standards. The rotors are timed exactly by helical gears and remain a fixed distance apart. As you heat them up they expand and the clearance between the rotors becomes less untill they begin rubbing and very quickly destroy each other and the case. Yes the case expands too but not as fast as the rotors so the case gets roughed up too. At $2000+ for a new street blower I think anyone would like not to have this happen very often.

And once again reality and the bank card take over. It's pretty easy to set up a single carb or as more often seen, pair of carbs to slosh enough fuel in to make great pile of hp too. Not real efficient but it works and it only costs about 1/4 of the EFI price. By and large most blower systems are for looks first and very high performance second. If it sounds tough and looks tough, it must be tough is the effect desired. You can easily make 600 hp with a 6-71 blown 383 SBC and roast virtually any tire you can put on very nicely anytime you feel the need, and the motor will be quite reliable.

Keep in mind that these -71's have been on hotrod motors going on 50 years now so a lot of the bugs have been worked out. What works and what does not work is pretty well known. I do agree that I'd like to see a better EFI that doesn't cost as much but there are a lot of parts required, special machining and a computer to integrate in to the system and a lot of testing and tuning time is needed so it all adds up.
 

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EFI Rules and Carbs Drool
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All good points bentwings. It really depends on your application. I've run this motor setup for over 7,000 miles on the street with no trouble at all. All it takes is some patience and an open mind and EFI can be done relatively inexpensively. Obviously, a drag motor or a high horsepower street motor is a different animal all together. I used a beat up old diesel blower for a reason, it was made to pump air so the tolerances were larger than a blower from XYZ that is "setup for gas" (plus i'm cheap). My engine fits into the "If it sounds tough and looks tough, it must be tough" as you say, but I can sure tell the difference when I'm making boost, so the system does add to the performance.

I used a stock multiport injection intake manifold and made an adapter plate for the blower. The injectors and fuel rails are tucked under the blower, but are still accessable without removing the blower.

Blower - cheap (I got for free but say $400)
Rebuild Kit - $100 (bearings / gaskets)
Drive kit - $600
Bugcatcher - $400
Megasquirt Computer - $500 (Includes harness and Accessories)
Intake - $400 + My Labor
Sensors / Injectors - Free (donor motor)
Fuel Rails / Fuel Lines / Regulator - $300

Granted, I started with an engine that was already fuel injected and had crank triggered ignition, so I had something to work with. Since I had a buddy give me the blower, I figure I ended up around $2,500 for the whole setup, which is a far cry from the $5,000 - $10,000 setups from the big names. Not bad when guys are paying up to $1,500 for just two Demon carbs.

The Megasquirt computer comes with an autotune feature which automatically fine tunes your fuel table while you drive. The best part is you can tune the engine and never pull out a screwdriver. I can adjust all fuel and spark parameters from a laptop. When I'm done, unplug it and I'm good to go.
 

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bentwings
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Oh that is beautiful.!!!! That's probably the coolest system I've ever seen. The work of a true hotrodder. I wasn't aware of the Megasquirt. I have to check this out.

Your system looks very nice and fits the application perfectly. I'm sure you have all the power you need. Not only that it has the proper 'look' to be fearsome. haha I can only guess how it sounds.

The one thing you didn't add to to list of needs was talent. That my friend you have plenty of.

It's a very clean appearing motor too. Love it.

You are right about the blower being an air pump. For your application it works fine. You took the exact steps necessary to make sure it stays in proper 'alignment' by rebuilding it. A pure stock one usually won't survive as they are usually pretty worn out by the time we see them.

My hat's off to you. Looks like some 'crow' for dinner today. haha

Keep up the good work. Come up to "back to the 50's" next summer. I'd love to see your rod.

Good work.
 

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EFI Rules and Carbs Drool
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Thanks for the kind words bentwings,

That means a lot comming from someone who knows thier way around engines. I was just trying to show there are alternatives and that EFI (and blowers) can be done on a budget with some research and planning. It's not for every application, but it's gaining popularity on the street.
 

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Great information going here.....I was going to chime in on the availability of affordable EFI if you have the time and dont mind doing some learning to make it all fit together, but looks like you guys got it covered.

I will also shed some light on the 16 injector deal. I would speculate this is because of the cost and availability of injectors that will flow enough fuel to feed and engine like that as well as tuning issues. The issue is that when injectors get too large it is difficult to get the engine to idle properly due to overfueling. With a fairly small amount of code and ECU can run on 1/2 the injectors up to a delivery point and switch to all 16 under power adjusting injector pulse width to maintain accurate delivery. If it is a WB equiped unit running with feedback loop it would make tuning an engine like this almost automatic.....which is sortof cool:)
 

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EFI Rules and Carbs Drool
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Yes, thanks TurboS10 for clearing that up.

Centerline said:
If I'm not mistaken they had 16 80 lb. injectors in that plate.
If that is true, then they have enough fuel flow for around 2,000 HP !!!!!!

According the Megasquirt online calculator, eight 55# injectors should be good to 750 HP. Eight 74# injectors would get you to 1,000 HP.


Lot of good information regarding the fuel side of EFI here:

http://www.megamanual.com/v22manual/minj.htm
 

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I gotta tell y'all... Arrowhead is my IDOL and was a true inspiration to me.

A lot has changed in 50 years, that's for sure. The use of injectors on top is, in my opinion, so that the person can use a computer to control the motor and squeeze the most out of it. Arrowhead and myself have taken the route of using what the modular 4.6 has to offer and built upon it. He went with megasquirt and I stuck with the factory computer and MAF system. Had I done it all over I would have started with Speed Density with a BigStuff3 controlling everything.

But this thread isn't about engine management directly so I'll save it for another one.

I've got my 6-71 running dry like Arrowhead because it was built to run this way. There are no teflon strips on the blower lobes so I don't have to dump fuel down from the top to keep them cool. That's why they run wet, by the way, to keep the teflon friction down to a manageable level.

That doesn't mean I *can't* add more from the top (as in a 300 shot wet system below my throttle bodies):




And I gotta say, it never gets old looking at big shiny belt driven hood scoops on cars! Old School ROCKS!

John
 

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EFI Rules and Carbs Drool
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Thanks for the kind words.

John,

How did you end up with your motor? Did you dyno it? How are your track times? I know you were shooting for some seroius horsepower and I'm sure everyone would be interested to hear some specs.
 
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