QJ tuning

turtlevette

The Turdle
Joined
Mar 24, 2008
Messages
1,492
Location
Marshfield, MA
I'm going to mess around with trying to get things running better. It detonates, backfires, and stalls under acceleration.

current setup
74 primary jets (stock is 75)
46 primary rods (stock)
unknown spring (i know its way too light I cut it at one time.)
CH secondary rods (stock i think)
long hanger (service hanger code V ?)

I'm going to go quite a bit richer to be able to switch back and forth between gas and E85
They say rule of thumb is go 10 sizes bigger on primary jets to run E85. If i go half way i might have a good compromise.
The biggest primary jets i can find are 79 which does that.

metering area calcs
metering area = jet area - rod area
existing = pi*(0.074/2)^^2 - pi*(0.046/2)^^2 = 0.00430 - 0.00166 = 0.00264
new = pi*(0.079/2)^^2 - pi*(0.046/2)^^2 = 0.00490 - 0.00166 = 0.00324
percent increase = (0.00324/0.00264)*100 = 22.7

stock = pi*(0.075/2)^^2 - pi*(0.046/2)^^2 = 0.00441 - 0.00166 = 0.00275
percent increase over stock = (0.00324/0.00275)*100 = 17.8


That's pretty rich but i can adjust the aneroid jet all the way closed for gas to minimize the richness. I still don't how much adjustment is there. It's designed to go from sea level to mountain driving. I would guess +/- 5% ?? a little more than one jet size.

I ordered the performance accelerator pump with ethanol rated rubber. The only difference is a stiffer spring behind the plunger.

I ordered a 5 spring set for the power valve and plan on installing something in the middle.

I ordered the shortest hanger and a long tip secondary metering rod code CK. The longer tip rods bring in full richness sooner. I'm wondering if the current long hanger coupled with the short CH rods are even getting to the last step on the rod??? The hangers can be bent to bring in richness sooner or later per air valve angle.

CH =0.0570
CK =0.0530

The secondary jets are non-removable 0.1350 thousands. Gives an area of 0.01431

0.01431 - 0.00255(CH) = 0.01176
0.01431 - 0.00221(CK) = 0.01210
0.01431 - 0.00152(DA) = 0.01279
0.01431 - 0.001320(CE) = 0.01299

0.01210/0.01176 = 1.0289 or 2.9% richer
0.01279/0.01176 = 1.0875 8.6% richer
0.01299/0.01176 = 1.105 10.5% richer

I just realized i messed this one up. I should have gone richer. The CK rod has a longer tip so full rich will come in sooner so there will be some tuning difference that may be noticable. I'll have to buy another set of secondary rods for alcohol that will bring it about 30% richer.

The cool thing about ethanol is that it doesn't detonate under lean conditions so it won't be that dangerous to play. I've actually run E85 with the current setup which should be way way lean but it runs surprisingly well. It takes some work to get it to idle nice. The mix screws need to be backed out 4 or more and idle screw bumped. I don't think it actually gets any richer after 4 turns.

With bigger primary jets the idle circuit should get correspondingly richer.
 
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I know nothing of what you trying to do, but I gotta ask, what are they selling E85 for up there?? seems you be pissing fuel like MAD so the cost would have to be really cheeeeeeeep.....

I just noticed a flag at the local BP station about a mile away....NO alky gas, 100% pure gas....4.37/gallon.....roughly a buck/gallon higher than the 10% crap they selling....a buck a gallon is a hell of a penalty to regain our 15% loss in the MPG....just not worth it....

:surrender:
 
There's a station that sells it in Canton about 15 miles away. I've done experiments before where i got the same hwy mileage as on E10. I think it's because i can run it real lean and advance the timing and it still makes enough power and doesnt detonate.

I need to go through the carb now anyway to avoid being too slow when i go to Mosport this summer.

We all like to play with these things constantly anyhow. The secondary rods and hanger are so easy to change guys may want to at least play with that.

When you compare E85 to race gas at 8-10 bucks a gallon, it looks real good.
 
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There's a station that sells it in Canton about 15 miles away. I've done experiments before where i got the same hwy mileage as on E10. I think it's because i can run it real lean and advance the timing and it still makes enough power and doesnt detonate.

I need to go through the carb now anyway to avoid being too slow when i go to Mosport this summer.

We all like to play with these things constantly anyhow. The secondary rods and hanger are so easy to change guys may want to at least play with that.

When you compare E85 to race gas at 8-10 bucks a gallon, it looks real good.

I thought that in order to get the power outta E85, you needed run a CR of like 14-1 or do a compressor of some type to get the effective CR up there, like 8 lbs boost....that's my recollection of what guys were saying some time ago anyway...

:gurney:
 
I've actually thought about building an engine for the Vette specifically for E85. While the power density is somewhat lower than straight gasoline, the octane rating is a lot higher - somewhere around 109 or 110 if memory serves. With the compression ratios you can run without knocking on that kind of fuel, the fuel useage is more efficient.

Those badly non-optimized "Flex Fuel" cars and trucks don't get great mileage on E85 because they aren't really designed to get the best advantage from it.

If E85 was available in more locations I'd probably go for it.
 
http://autoplicity.com/products/379...=GSNOFITMENT&gclid=CLOsk9Sc9K8CFYeo4AodehfvXA

INN-3821.jpg


I just bought this to aid in my tuning. I selected it because i don't like digital gauges and it will look similar to my silver faced autometer guages.
 
You need a lot more alcohol to get the correct stoichiometric ratio. This means you will use a lot more fuel. You have to take that into the equation.

If the engine is not built to use the higher octanes of this fuel, you're only going to use more of it and no extra power.
 
You need a lot more alcohol to get the correct stoichiometric ratio. This means you will use a lot more fuel. You have to take that into the equation.

If the engine is not built to use the higher octanes of this fuel, you're only going to use more of it and no extra power.

I'm not sure i agree with that, but we'll see. Right now the car runs adequately on E85 without even rejetting. I agree with the premise that for maximum efficiency and power you need a purpose built engine but that is not what i'm shooting for. I shooting for a flex fuel C3.

No more shitting on E85. This is a thread about QJ tuning with E85 thrown in as "extra credit". TT will probably come in and tell me my LM-1 sensor will not work with E85. There are fudge factors below.

http://e85forum.com/about94.html&sid=6047110803f9f1c3aebc3bdff6d6d4c0

The actual value of AFR depends on the hydrocarbon. For the case of gasoline and ethanol mix, the AFR stoich point moves (assume gasoline has H/C of 1.65, O/C=0):

100% gasoline = 14.191 AFR
90% gasoline, 10% ethanol = 13.667
50/50% mix = 11.569
15%gas, 85%ethanol = 9.773
100% ethanol = 8.946
 
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