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Discussion Starter #1
I know it has been probably covered but i cant find it.
I have it injecting into the top of the roots blower.
Is it better to inject it into the manifold after the blower?



Lets say that the blower demands 1000cfm at max power.
Normally it would suck it through the carburettor.
The carburettor in turn would venturi in the alloted amount of fuel dependant on the tuning of the carbuettor in order to achieve the desired exhaust gases to give a good air/ fuel ratio, and optimum power.
Now......
If we feed some of the blower demand by direct injecting into the top of the blower the equivalent to say....200cfm of injectant, then the blower would now only demand 800cfm from the carbuettor.
Therefore the carbuettor would now venturi in the alloted amount of fuel dependant on the above tuning scenario, but at 800cfm and not 1000cfm.
And then make about the same power.

If we injected below the carbuettor then the blower would still demand 1000cfm through the carburettor AND the engine would get that PLUS the injectant

Any thoughts would be appreciated.
 

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Discussion Starter #4
Thanks for your reply.

I am currently injecting 650cc/minute of 50/50 water/meth into the top of the blower but am only making 8Hp extra.
355 sbc at 8.5:1 Comp ratio
Forged pistons, hyd lifters, 1.6 roller rockers
B&M super street charger cam,
duration at 0.0065 lift: Intake 282 deg, Exhaust 292 deg, Overlap 59 deg.
duration at 0.050 lift: Intake 234 deg, Exhaust 244 deg, overlap 11 deg.
lift at cam: Intake 0.3254", Exhust 0.3400".
lift at cam: Intake 0.488", Exhaust 0.510".
Edelbrock Performer RPM heads, 64cc chambers.
MSD 6BTM ignition. 17deg at idle, 35deg total, all in by about 2400rpm
boost retard set to "0" when injecting on premium pump gas.

B&M 162 at 2.4:1 OD, making 6 psi, 8psi with water/meth through it
QFT 850 blower carb
Hooker super comp headers, twin 2.5" system. "x" pipe, Hooker Areochamber mufflers. turn downs before diff.

I have posted some dyno plots here. http://www.cardomain.com/ride/3106629/1968-chevrolet-camaro

I am wondering if I am simlpy injecting at the wrong place or just not enough.

We noted the IAT without the injection it was 86C at max power and with the injection it was 49C.
Also at 5500rpm there was slight detonation.
We were unable to add any timing, which is what I was expecting to do.... more timing.....more hp.

Any help would be gratly appreeciated.
I have a meet at the end of this month and was hoping to have this well sorted before then.


Wayne
 

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my 350 picked up 50 hp over pump vs pump and meth/water, but only 10 more than race fuel vs pump and meth/water.
I make about 14.5 pounds of boost with no detonation on pump gas, I also run the btm and run 36 total with a third of a degree being pulled per pound.
As for the amount of meth/water, I cant say how much I used the big jets supplied and the controller varies the amount according to the boost, its on at 4 pounds and full spray by 8. I was happy as I can run pump fuel with a race fuel tune. so are you saying with the pump gas and meth you cannot run a race gas tune?
or did you just go from race fuel to pump meth? and keep the tune the same, or was it always pump gas?, on the dyno I had to go down one jet size in the primaries to achieve the same a/f as before the meth. also mine is spayed under the carbs.
 

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Anybody have tenp sensors for IAT above the blower and in the intake manifofd??Is it directionally proportional when the water / meth is injected.Would it pay to use a perimiter plate for thr meth injection??
 

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u should pull some timing out still. maybe half per pound. you could spark knocking

i would say if you didnt have meth working you would have detonated and blew head gasket
 

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Discussion Starter #8
Thanks for your replies guys.

We had a structured day.
base run on pump gas.
pump gas plus water only
pump gas plus water/meth 50/50

A few of the dyno plots are here...... http://www.cardomain.com/ride/3106629/1968-chevrolet-camaro

I wonder if it is the plugs complaining. they are set to 0.035" gap, dont aske me the heat range but they looked ok.
We also reduced the size of the secondaries to lean it up a bit as the AFR was too fat with the water/meth.

Still puzzled
darined fuel tank and did avgas only
then avgas plus water/meth 50/50
 

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how good is the meth spraying. if the pressure is down, for some reason, on meth pump it might not have a good pattern.
 

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Discussion Starter #11
Hi guys
Thanks again for all your input.
I have tapped the jets into the top of the blower housing. One just in front of the carb adaptor and one just behind it.
I am using an Aquamist system which maintains 160psi at all times and if there is a flow problem I get a failsafe warning si I dont believe it is a flow failure problem.
I can only guess that I either need to go 100% methanol or 100% water or stick more in at 50/50.
I am guessing though, someone here should know what works and what doesnt.
Cheers
 

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I run 50/50 as well. I have 4 jets, two under the rear carb and two under the front. I machined my carb adapter plate and installed the nozzles on each side. The kit I have is an old AIS (Alcohol Injection Systems). I run 12psi of boost on 91 octane and start spraying at 6psi. Like I said I have an old system so no controller, it's either on or off.
 

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Best place to inject on roots style superchargers is right through the blower. Blowers like this need A LOT but when the jetting is right. You can literally feel the difference on the outside of the blower housing after a pull on the dyno.

Rodney
 
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