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Discussion Starter #1 (Edited)
Hey guys I have a question for you. I have been thinking about running a dry 75 shot on my truck. From the reading I have done people usually set this up to blow over the MAF to have the computer add the needed fuel.

My problem with this is that when I got my road tune from limeswap at SESM I thought he said it looked like my MAF was almost maxed out (or something along those lines). Would I have an issue running the 75 shot across my MAF like this? Would I then need to run a wet shot instead of dry (assuming my MAF is maxed)? Is there a different way I could run the dry shot? Or would the PCM automatically switch over to speed density?

Also the stock 3.5 fuel system should be adequate still with a 75 shot?

Thanks for any help guys.

@limequat
 

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Re: dry 75 shot, maxed MAF?

i wouls just run a wet shot. I ran a wet 75 HP shot on my nissan hardbody back in the day. Never had an issue. I like the idea of a wet since you probally wont ever set it up too lean
 

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Discussion Starter #3
Re: dry 75 shot, maxed MAF?

Thank you for your response but from what I have read on here and around the net I think a dry shot would suit me best and is my first choice. I am not opposed to a wet shot, just saying as of right now I am liking a dry shot.
 

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Re: dry 75 shot, maxed MAF?

Hmm, I don't remember the context of that conversation. But I looked back at your logs and you seemed to pulling a max of about 25 lb/hr of air. The maf goes over 40 lb/hr, so in theory, I think the MAF would have the capacity for a 75 shot.

I've never considered that the MAF can understand the amount of oxygen in a NO2 shot. Do people do this with success?
 

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Discussion Starter #5 (Edited)
Re: dry 75 shot, maxed MAF?

Hmm, I don't remember the context of that conversation. But I looked back at your logs and you seemed to pulling a max of about 25 lb/hr of air. The maf goes over 40 lb/hr, so in theory, I think the MAF would have the capacity for a 75 shot.

I've never considered that the MAF can understand the amount of oxygen in a NO2 shot. Do people do this with success?
05_quick4door mentioned it at least once with a quick description here. That post is located on page 2 of this thread

I thought I remembered something about the maf being maxed and that I would be fine as long as I wasn't going to turbo or something but I could be dreaming?

edit: I was also thinking if I did the pre-maf dry shot I could mount the nozzle in the end of the AEM dry flow filter I have with my intake so there is plenty of time for the air/n20 to mix/atomize? Apparently some people have had trouble with too close of a nozzle position freezing or damaging the MAF.
 

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Re: dry 75 shot, maxed MAF?

I am not sure how our trucks are set up. However, in most dry setups, you also do something to increase fuel pressure, or someother way to increase fuel when the NOS is activated. NOS does not break down into O2 until its heated, so i dont know how the MAF would knwo how much fule to add. A wetsystem is really easy to set up. If you just put a fogger nossel in a TB spacer, you are golden.
 

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Discussion Starter #7
Re: dry 75 shot, maxed MAF?

I am not sure how our trucks are set up. However, in most dry setups, you also do something to increase fuel pressure, or someother way to increase fuel when the NOS is activated. NOS does not break down into O2 until its heated, so i dont know how the MAF would knwo how much fule to add. A wetsystem is really easy to set up. If you just put a fogger nossel in a TB spacer, you are golden.
The idea of spraying through the MAF is that: the MAF reports how much air is flowing past it and the PCM would then compensate for increased air flow (from nitrous) by adding more fuel. You would not need a fuel pressure trick or similar.

That is according to what I have read around the web, LS1tech and here included.
 

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Re: dry 75 shot, maxed MAF?

I thought I remembered something about the maf being maxed and that I would be fine as long as I wasn't going to turbo or something but I could be dreaming?
Oh, yeah, yeah we were talking turbo a bit.

Yeah for a turbo you'd need a larger maf tube for anything more than a few PSI.
 

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Re: dry 75 shot, maxed MAF?

So I read some of the nitrous thread. It's the cooling effect from the NO2 decompressing that fools the MAF.

I would be very concerned that this effect is not repeatable. Could it happen that you hit a bump, the nozzle moves a bit, the shot misses the MAF and you go lean?
 

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Discussion Starter #10
Re: dry 75 shot, maxed MAF?

So I read some of the nitrous thread. It's the cooling effect from the NO2 decompressing that fools the MAF.

I would be very concerned that this effect is not repeatable. Could it happen that you hit a bump, the nozzle moves a bit, the shot misses the MAF and you go lean?
I would think that would be possibly if you were spraying directly across the MAF but if you had it further down the pipe in front of the maf (allowing more time for air/n20 to mix) I would imagine it wouldn't be an issue.
 

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Re: dry 75 shot, maxed MAF?

why not call a nitrous company and ask them what they did to design their system to work with MAF. like what is best to do, and how to set it up. this way you get their info from the people who designed it, and not some people like me guessing at what might and might not destroy your truck...?

their info is fast, correct, probably has downloadable instructions and free..
 

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Re: dry 75 shot, maxed MAF?

I would think that would be possibly if you were spraying directly across the MAF but if you had it further down the pipe in front of the maf (allowing more time for air/n20 to mix) I would imagine it wouldn't be an issue.
problem is, if you go too far down, the NOS charge can heat up, making the MAF not add as much fuel. Basuicaly its just the cooling of the NOS that is addign the extra fuel. the MAF is not actually compensating for the NOS.

Agin, i am limited on my knowledge on these trucks, as i am a new owner. But, if you want to do NOS, why not a wet system? It allows for better tuning and is safer, atleast from how i see the dry system depending on the MAF to add the correct amount of fuel.
 

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Re: dry 75 shot, maxed MAF?

and for a heads up, i maxed the maf at about 10-11 lbs on a 3.5 with a 3" pipe.

so you have some headroom
 

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Discussion Starter #16 (Edited)
Re: dry 75 shot, maxed MAF?

Sounds like a hokey way to run nitrous to me. Good luck that.
Way to actually add something to the discussion. Why not at least make a suggestion for how you would run it?

Just search around, plenty of well known companies make kits that utilize the MAF to add fuel. Just because you don't do it/haven't heard of it doesn't mean it is "hokey."


problem is, if you go too far down, the NOS charge can heat up, making the MAF not add as much fuel. Basuicaly its just the cooling of the NOS that is addign the extra fuel. the MAF is not actually compensating for the NOS.

Agin, i am limited on my knowledge on these trucks, as i am a new owner. But, if you want to do NOS, why not a wet system? It allows for better tuning and is safer, atleast from how i see the dry system depending on the MAF to add the correct amount of fuel.
Yes and no. According to the reading I have been doing the n2o separates and burns at like 572 degrees but the expansion of the n2o as it is injected does generally have around a ~70F degree cooling effect which also increases power (like you said).


On another note: I may just go wet shot for the fact that there is less uncertainty about whether it will be fueled properly. With a wet kit would it be better to shoot before or after the the throttle body? I was thinking of using a TBS and tapping it for the nozzle/s which would be after the TB.
 

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Re: dry 75 shot, maxed MAF?

I would have made the correct recommendation, but since that was already made in the first response and you shot him down, I figured you already had your mind made up, and weren't really looking for advice.

I'm glad to see that you agree with me though, and have decided not to do it. And yes, a dry shot before the MAF without any other compensation is hokey.
 

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Re: dry 75 shot, maxed MAF?

also, what does one do about timing? I would not mind a 75 shot on my truck. On my nissan, i dialed back the distributor back a few degrees before i went to the track, or cruising around, just to be safe. I melted a few sets of plugs from having to much timing. Good think nissan engines are bullet proof
 

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