Tuning chnages

I am fairly new to blown alcohol.

On Thursday night I went and test ran my boat on a local lake. It ran super and made a ton of power. I made two runs and was getting low on fuel so I decided to quit for the night. I went and got another barrel of fuel the next day, then drove 6 hours south to race the boat on Saturday. I did not change anything.

The boat was lazy, popping out of the exhaust, bogged out of the hole and basically ran like crap.

Am I missing something here? Maybe a change in fuel quality or specific gravity? Any ideas?

 

check the fuel somebody neer me got e85

 

Popping sounds way too lean...temp/humidity/barometer all have a huge effect on blown alcohol motors. You need to keep records of all these things when making a lap so you can refer back to the records to replicate performance in any given weather condition

 

I am sure it was not too fat, the oil looks perfect and I did not see any fuel coming out of the zoomies.

The elevation at home is 1362 and the elevation where I was racing was 774. That is the only change other than the fuel.

I got the fuel from the same place that I got it last time and am positive that it is methanol.

I have not had to write anything down yet, because I have not tuned this thing one bit yet (as far a jetting) Any insight or advice would be great.

Thanks, Ryan

 

The spark plugs probably have a little more than an hour of run time on them, and look good in my opinion. The plug wires are less than a week old, as well as the coil wire. I just had the mag serviced by FEI.

The valve springs look good and were new this early summer. I dont think the engine has 2 hours on it yet, including the dyno time.

I dont understand what could make this engine run so completely different literally 36 hours later.

 

I will try some new plugs and see if it makes a difference in how it runs. How often do most top alcohol guys change their plugs?

 

Maybe my problems are due to my plugs. I removed them and they dont look all the bad (to a gas guy) but did notice a few of them with some discolored porcelain. Maybe the plugs are doing something similar to carbon tracking?

Also, I had my plug gap set at .020, I will narrow it up a bit. What is a good heat range plug to use. I am using NGK r5671a-8 plugs right now.

Thanks again, I really appreciate the help.

 

What type of ignition are you running? When I had a marginal mag SMIII I would kill a set of plugs in 1-2 passes. First pass would be strong, next one not too bad, third pass the engine was popping /bogging and I was getting fuel out the headers. Plugs would look fine but they were done. A fresh set would put things back where I was in the first run. Rebuilt the mag and it was way better, at 27psi it still was not enough mag however.

Corey

 

I am running a sprintmag II, it was just serviced at FEI. I will narrow my plug gap up a little bit and change to a cooler plug.

Thanks for all the help!

Ryan