As the title states, I'm trying to figure out if I really need to be running methanol, or if I have it up too high, or what.

On my LT1 I have TexasSpeed long tube headers, A&A V3 Ti with the 3.6" pulley at 9psi. Alky kit single nozzle.

Now, this dynoed out at 669/603 with SAE correction:



However, I live at high altitude and on that day (87 deg F, 24 in-Hg baro, 32% humidity) the SAE correction level was 1.3, and the car really only put down 515/465:



I had the car dyno tuned with my methanol kit installed, however it did have a slight leak at the time (unbeknownst to me) and didn't build full pressure - the light never turned green. Further, I'm not sure if the tuner changed the methanol setting from gain of 4 when he did his tune.

Afterwards I took it to the track, and only did three runs, because after the third run, the car was super low on power -- this is when I found the methanol fitting was loose, and I blamed my poor track performance on that. Do note that I have a warning set on my dash control unit to chime when my knock retard timing goes above 0 degrees, and this never happened.

So, this leaves me with the following questions:

1. Firstly, should I be running methanol at the power levels I'm making? If so, how do I know if my gain is set too high or too low?

2. When the car had no power at the track, why? I had assumed the lack of methanol meant increased IAT temps which means the computer pulled timing. Is this the case? Or is it possible my knock sensors are disabled and something else was happening? How can I find out (see #4)

3. Now that my methanol fittings are tight, and it goes green when I hit the test button, how can I tell if I need a re-tune?

4. What data points can I log in order to see if my tune and car is healthy, in regards to timing, fuel, and injector width? (Keep in mind I have the ability to data log with a DiabloSport Trinity, but I do not have a wide-band o2 sensor installed.)

5. I drive only at my altitude, however, it is conceivable that I head to sea level with the car to drive it. If this is the case, what kind of things should I keep in mind there, considering the questions above?

Any guidance or comments you guys can provide would be awesome.

Thanks!

 

I will try to answer as many as I can:

1: yes. Gain should be set around 6 from my experience. If you need more or less meth, you change nozzle size.

2: what was the temp outside at the track? This is important to know how the car should act in regards to heat soak.

3: you will need to retune. Are you running 100% meth or a mix of 50/50? If you are running 100% then you are supplementing Meth for fuel in the tune. Now that your meth is working correctly, you are getting more meth, i.e. more fuel. This affects your A/R throughout the power band. You're probably running rich at WOT now.

4: get the wide band installed. Like yesterday. That's going to tell you how rich or lean you are running in regards to overall health. I'm not sure if you can garner any useful info for this specific concern through the Diablosport.

5: if you drive the car to an altitude that is significantly different you will need to have the tune adjusted I believe since the atmospheric pressure is different when major altitude change is a factor.

Ant

 

^Just a quick clarification, in case I wasn't clear enough: I *am* at high altitude, my car only makes 515, most people would say this is not enough power for methanol.

1. What makes you say 6?

2. IATs were acceptable. Would a heat soak cause a more than two second reduction in quarter mile time?

3. If i'm running rich, why not just run less meth, since obviously I have enough fuel....

4. Do I need to add another wideband o2 sensor, or can I replace one of the existing lambda sensors with a wideband, and change some tuning?

5. Yes, that's really my main point: altitude affects barometric pressure. However a re-tune to change altitudes seems strange to me, one would think the fuel trims could accommodate for altitude / baro changes.

Thanks for the info!

 

You know, sometimes it just helps to read the manual. According to the Fine tuning guide that came with the C7 alkycontrol instructions...

I guess that makes me wonder about the initial reason for the knock. Obviously methanol will help prevent knocking that is due to high iat or due to lack of fuel, but will it help with knock due to too much timing? I suppose, added octane and all that...

 

515 does seem low with meth.

1. I say 6 because that's what most people have their set at from what I have read countless times on here. Also it's what I have mine set at. If I remember correctly the gain **** doesn't necessarily control the amount of meth sprayed really but controls the "ramp up" of the pump/spray. Ramping up faster does mean more meth but this also affects the tune because the tune is set to expect a certain amount at each point throughout the powerband.

2. If IAT was in check, then no, I wouldn't think 2 seconds. What was your time? And do you know anyone else with similar mods in a C7 that ran at the same track? That would give you a good baseline to compare from.

3. It is not recommended to turn the meth down past a certain point. If you do, there will not be enough pressure to atomize the spray. If you want less meth, you simply move to a smaller nozzle.

4. A wideband must be added. You cannot use the existing o2's or their bungs. The wideband needs to be in front of all o2 sensors in the exhaust. In ARH long tubes, there is already a bung welded in just for this.

5. That may depend on the tune and the intelligence of this ECM. I'm not sure if it can adjust that much when boost is involved. It can adjust in normal NA C7's but now we are changing the air pressure significantly by adding boost. The Z06 I'm sure can accommodate but obviously that's a different tune entirely lol.

Ant

 

I am 99 percent sure mine is a hair above 4.

 

Your car makes a lot more power than what it shows on the dyno do to the elavation... this car needs meth without a doubt on a 3.6 pulley and boltons.

if you didn't see any knock I would bet the knock sensors are probably turned off or really desensitized.

 

^ How do I tell? Can it be checked with data logging?
You mean a lot less, right? SAE dyno shows 670 horsepower, but I know I'm not making anywhere near that due to quarter mile times.

 

you need fuel to burn the oxygen or you need the oxygen to burn the fuel. they burn together at a specific ratio.

the amount of power you make is directly related to how much burnable air (oxygen) you have. if you have less oxygen then you need less fuel. if you have less oxygen you make less power. if you make less power you need less fuel.

corrected numbers don't matter unless you're bench racing.

 

^Yeah I thought so, higher altitudes, less oxygen, less fuel, less power than sea level equivalent.

Which would also lead me to believe less methanol requirements.

 

Consider this:



Using the example above, and knowing that the 9psi of boost measured at MAP sensor (minus Barometer), absolute manifold pressure at my altitude is 20.7psi (143 kpa). This setup at sea level would see a max absolute manifold pressure of 24.7psi (170 kpa).

At the speed at which these engines flow, I'm sure that's a lot of air that I'm not getting compared to those at sea level. I believe one could say, at least for air to fuel ratio purposes, I'm running equivalent of 6psi boost.

Those familiar with tuning the c7 can probably say how much injector pulse width is needed for a MAP reading of 143 kpa at WOT, and if the stock injectors can do that without issue.

 

on a DI engine you want to keep your IPW below 6 but preferably under 5 any time you are WOT.

IPW is controlled with injector timing (to a point....that a lot of tuners are surpassing and don't realize it) and fuel system pressure/volume.

If you are going over 6ms (when properly tuned) then you need meth.

 

Excellent info, thanks Higgs.

For any random boosted tune, could you say exactly how much air the MAP / MAF sensors are seeing when commanding that 6ms timing?

 

Hmm...that's hard to do because you want that 5 - 6ms at 1000 or 650 and there are plenty of tuners who run it up to 10ms+ not knowing what is actually happening in the cylinder.

But, usually 65 lb/min will put you around 650 crank and 100 lb/min around 1000 crank. Of course there are other variables like spark and an accurate airflow model that dictate how close that rule of thumb is.