Atacc jetting ?

[rfield]

Just installed Atacc, vented on the outside of the airbox on my IQR 800 monoblock conversion, 136 inch with 2 inch paddle, oil injection. I have 470 mains in now and heading and heading on a trip and wont have a chance to really run the sled before I go, it will be between 0 and -15 celcius and will be running between 0-2000 ft and running 91 octane. Has anyone run the 470's in these conditions ? Should I go with 490 mains or will I be ok with th 470' s ? Thanks

[rfield]

ttt

[RIPSASS]

I have the exact same setup as you. 800-mono conversion, 136"x2" DynoPort single, ATACC, 0-3000'.
Running 490's and lately it's been around 0 to -10 below. Based on plug color and wash I wouldn't go any leaner in these temps.
It was probably ok before the DynoPort pipe (stock pipe with BMP "mod") but the DynoPort pipe is making tons of power and moving a lot of air.
But I'm also running a high comp head from Power Addiction Racing (13.5:1 ratio) and 100 octane AV gas, so it has a little bit of a safety margin there from the leaded (and higher octane) fuel.

I'm also still running a stock airbox too. If you are running pods, or a pipe that doesn't flow as well you should be good on 470's. But otherwise I'd go 490's just to be safer.
Besides the ATACC will compensate out 90% of it anyway if you are fat.

[peterepeater]

Originally Posted by RIPSASS

I have the exact same setup as you. 800-mono conversion, 136"x2" DynoPort single, ATACC, 0-3000'.
Running 490's and lately it's been around 0 to -10 below. Based on plug color and wash I wouldn't go any leaner in these temps.
It was probably ok before the DynoPort pipe (stock pipe with BMP "mod") but the DynoPort pipe is making tons of power and moving a lot of air.
But I'm also running a high comp head from Power Addiction Racing (13.5:1 ratio) and 100 octane AV gas, so it has a little bit of a safety margin there from the leaded (and higher octane) fuel.

I'm also still running a stock airbox too. If you are running pods, or a pipe that doesn't flow as well you should be good on 470's. But otherwise I'd go 490's just to be safer.
Besides the ATACC will compensate out 90% of it anyway if you are fat.

How are you doing on fuel economy with this set-up?

[RusseauRestoration]

Originally Posted by RIPSASS

I have the exact same setup as you. 800-mono conversion, 136"x2" DynoPort single, ATACC, 0-3000'.
Running 490's and lately it's been around 0 to -10 below. Based on plug color and wash I wouldn't go any leaner in these temps.
It was probably ok before the DynoPort pipe (stock pipe with BMP "mod") but the DynoPort pipe is making tons of power and moving a lot of air.
But I'm also running a high comp head from Power Addiction Racing (13.5:1 ratio) and 100 octane AV gas, so it has a little bit of a safety margin there from the leaded (and higher octane) fuel.

I'm also still running a stock airbox too. If you are running pods, or a pipe that doesn't flow as well you should be good on 470's. But otherwise I'd go 490's just to be safer.
Besides the ATACC will compensate out 90% of it anyway if you are fat.

Hello RIPSASS. I have almost the same set up as you but my Power Addictions head is 12.5 to 1...I have been running a mix of 93 octane pump gas (75%) and 112 Polaris Race Gas (75%). I run oil injection and mix the gas 32:1. I run 500 Main Jets at a 103 Air Density.

Anyway, I see that you really like your ATACC and I was wondering if you would recommend it for the IQR with 800 Monoblock conversion.

I always find myseld re-jetting to make sure it is running at its optimum but I would really like the autocompensating feature of the ATACC.

Can you eloborate a bit on the ATACC...Any Pro's and Cons?

Thank You

-Scott

[akiqpilot]

Scott

The ATACC works very good. After installation and some slight tuning it requires almost no further attention. For the late model IQr sleds you do have to add a "T" and a 1 way check valve to the vent hoses between the carbs. This prevents fuel droplets from accumulating between the carbs and disrupting the signal from the ATACC and the float bowl. Peterepeter has one on his IQr set up with the ATACC and may be able to explain it a bit better.

The check valve and "T" is available through Holtzman when you buy an ATACC.

I built another IQr monoblock out of an '10 this fall. It's very similar to RIPASS's motor. Dynoport Single full exhaust, 13.5 Power Addiction Head, Port matched cases, Carbs with .9 PAJ, The sled totally rips. Current set up is this:

100Low Lead AVGas.
Timing on G or F depending
430 Main Jet
Needle in position #2.
55 Pilot Jet
Fuel Screw 2.25 turns out

And like I said. The motor rips, wish I had a dyno I am sure it's making nearly 170 HP.

[peterepeater]

Originally Posted by akiqpilot

Scott

The ATACC works very good. After installation and some slight tuning it requires almost no further attention. For the late model IQr sleds you do have to add a "T" and a 1 way check valve to the vent hoses between the carbs. This prevents fuel droplets from accumulating between the carbs and disrupting the signal from the ATACC and the float bowl. Peterepeter has one on his IQr set up with the ATACC and may be able to explain it a bit better.

The check valve and "T" is available through Holtzman when you buy an ATACC.

I built another IQr monoblock out of an '10 this fall. It's very similar to RIPASS's motor. Dynoport Single full exhaust, 13.5 Power Addiction Head, Port matched cases, Carbs with .9 PAJ, The sled totally rips. Current set up is this:

100Low Lead AVGas.
Timing on G or F depending
430 Main Jet
Needle in position #2.
55 Pilot Jet
Fuel Screw 2.25 turns out

And like I said. The motor rips, wish I had a dyno I am sure it's making nearly 170 HP.

As far as T'ing the vent lines...you can block them or t them with the one way check valve. The advantage of T'ing them is when the sled ends up on it's side or upside down (which is often the case), the carb has a chance of draining off some of that excess fuel when it floods. Get back on a level plane, hold the throttle wide-open and it'll usually start with 2-3 pulls. It won't take as long to clear out the rich-running condition either. The purpose of the check valve is to prevent the carbs from sucking in air, thereby throwing off the vacuum sensing ability of the ATACC.

As far as running quality and ease of tuning (elimination of tuning once you get it dialed), I'll never run a carb sled without one.....ever

AK- You mention you're running 430's on that '10 800....I assume this is a NON-ATACC sled? If so, and I'm just throwing this out there, one would assume you could easily run 460's on an ATACC w/ the 800mono vs. the 490's? My only logic is you run around a 380 on the 600 in say...10F. Therefore, a 410 will provide enough fuel for -25F (which is what the ATACC calls for), which is a rise of 3 main jet sizes. If you're safely running 430's @ 10F, on the same scale....would 460 be suitable? Of course one can never overlook plug readings and piston wash, but I ended up @ 410's w/ my ATACC on my 600 based off you're suggestions of 380 w/o an ATACC, and my sled is dead-nuts on as far as tune. 490's just sound so......excessive, like 6mpg excessive.

I would also like to mention that going from the 420's on my ATACC to the 410's, combined with a 98octane blend and timing on E, netted me a 3.5mpg increase. I'm gonna start a new topic based on this.

[RusseauRestoration]

Thank You Tom and Peterpeater.

I have probably shared my set up on this from "900 times" but I want to review it here once more and I would appreciate your advice on the inital set up for the ATACC

-2008 IQR with 800 Monoblock conversion
-Dyno Port Single
-Power Addictions 12.5 to 1 Head
-I Ride in Michigan 0 to 1000 ft
-My baseline jetting is a 500 at a 103 Relative Air Density
-I run a mix of 75% Polaris 112 with 25% 93 which calculates to 98 Octane
-I run oil injection and I mix the fuel 32:1...Some have said I am "wasting oil" but I really don't care as I want to error on the side of caution for lubrication. Also this is how I arrived at my baseline and my understanding is that adding oil to the gas (pre-mix) has an effect of "leaning the jetting"
-I run the timing on D...I have actually never even tried it on E. Can someone please tell me how much if any I am gaining running on D vs E.?? What are your thoughts.
-My needle clips is on #2.
-The Fuel Screw is 1.875 to 2 turns out.
-I am running a .7 PAJ. What is the advantage of the .9 PAJ
-Stock Pilot Jet
-68 Gram Clutch Weight
-140/330 Primary Spring
-64/40 Helix...I do not remember the secondary spring off the top of my head...I think it is a 160/280
-Gearining is 39/22 (1.77 Ratio)
-Sled Pulls consistent 8200 RPM....Dyno Port says it should run 8100 to 8300 RPM

So considering all of the infro above. What would you change (if anything) from this set up with NO ATACC and what would you change as a baseline set up with an ATACC?

Any help, ideas or thoughts are very much appreciated.

Thank You As Always

-Scott

[peterepeater]

Originally Posted by RusseauRestoration

Thank You Tom and Peterpeater.

I have probably shared my set up on this from "900 times" but I want to review it here once more and I would appreciate your advice on the inital set up for the ATACC

-2008 IQR with 800 Monoblock conversion
-Dyno Port Single
-Power Addictions 12.5 to 1 Head
-I Ride in Michigan 0 to 1000 ft
-My baseline jetting is a 500 at a 103 Relative Air Density
-I run a mix of 75% Polaris 112 with 25% 93 which calculates to 98 Octane
-I run oil injection and I mix the fuel 32:1...Some have said I am "wasting oil" but I really don't care as I want to error on the side of caution for lubrication. Also this is how I arrived at my baseline and my understanding is that adding oil to the gas (pre-mix) has an effect of "leaning the jetting"
-I run the timing on D...I have actually never even tried it on E. Can someone please tell me how much if any I am gaining running on D vs E.?? What are your thoughts.
-My needle clips is on #2.
-The Fuel Screw is 1.875 to 2 turns out.
-I am running a .7 PAJ. What is the advantage of the .9 PAJ
-Stock Pilot Jet
-68 Gram Clutch Weight
-140/330 Primary Spring
-64/40 Helix...I do not remember the secondary spring off the top of my head...I think it is a 160/280
-Gearining is 39/22 (1.77 Ratio)
-Sled Pulls consistent 8200 RPM....Dyno Port says it should run 8100 to 8300 RPM

So considering all of the infro above. What would you change (if anything) from this set up with NO ATACC and what would you change as a baseline set up with an ATACC?

Any help, ideas or thoughts are very much appreciated.

Thank You As Always

-Scott

If you're mixing 75% 112 to 25% 93, your octane is gonna be 107. You're wasting a TON of $$$ right there. Use this:MotorSports Racing Fuels - Racing Gas - Nitromethane - Methanol - Racing Lubricants - Additives - Race Fuels
And what they're telling you is correct about the oil. 40:1, 42:1 is plenty.

[RusseauRestoration]

Thank You Peterpeater.

How I arrived at the 98 Octane is that I used an On Line Fuel Octane Calculator that Tom (AKIQPILOT) gave me.

What are your thoughts on my general set up and what would be a good starting point for the ATACC?

Thank you again for your response and your help

-Scott