The 5ive-t on meth thread

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
@TODD Thanks for the added info I greatly appreciate it. From your experience is it worth going to glow plug? Does it advance the ignition event further than timing the flywheel? Just curious about the glow plug
 
Except to maybe loose weight from ignition system. Not really. That engine was heavy so I did what I could to get it lighter. I had some notes i found. Go heavy on oil. If not, possible failures maybe happen to upper and lower rod bearings. This will also depend how hard and long you run it, but it needs a lot more than what you used to.
 
Also keep in mind if you didn't know. You will need to run gas through it as was recommended earlier. Engine will rust up if not. If you didn't know this already? If you run just as hard as you do gas? You will have roughly 1/2 the run time before refilling. Alky is roughly 2 times the fuel burn 14:1 gas and 7:1 on alky a/f ratio.
 
@TODD thanks for the info and yes I was aware of the corrosive nature of alcohol. Before I introduced nitro to the engine I was able to see how the run time got significantly decreased. I was told to run a wt-257 carb as it will be good without needing to modify the jetting. Am I still using the 11mm restriction plate or do you have any advise on what restrictor plate to use?
 
That was an issue for us too when we did it on our newer engines. The Walbro 488 that was supposed to be for alky didn't work for us and from what i hear didn't work well for others.. We spend pretty much all our time at 18,500 rpm plus and finding something to work up there is an issue. We gave up on it because a few people liked the idea but everyone else poo pood the idea. 257 i don't know if it will work? Maybe for you but if you running high rpms constantly it can't keep up. Issues is fuel inlet needle on it. Some people say they work fine, but if are able to push it too the limit and hold it there? You will see it will not work. Pig rich to try and make it run on top but super dog rich when you not there. That why 990 and 929 came out. Same carb but has shorter fuel inlet needle.
 
Last edited:
@TODD Thanks for the info, I have the seaducer with the trevor simpson reed and an updated esp top end from doug. The reed and compression is there for me to benefit off methonal so I plan on atleast trying it. Also the trevor case let's me have -10/+10 degrees of timing advance without messing with the flywheel key. Seems that these oxygenated fuels have their place but for practical use in rc it's a marginal gain and it's been alot of reading and trial and error that seems not to be worth the effort and cost.
 
Rep732 typing too fast earlier and not thinking enough. 257 has longer fuel inlet needle which is more mass. Compared too 929 and 990. Pretty much all current carbs have short inlet needle in them. They finally listened I guess when we kept telling them what the issue was.
 
Thanks for that. So i take it the wt-257 has some merit with being able to flow more fuel.

I do find it interesting that a carb running gasoline can be overly rich if you keep winding the needles out and you can see the result.
For alcohol you can pretty much pull the needles all the way out and still not have enough fuel for it to obtain the right afr. I get it that the alcohol carries oxygen with it but it's still a liquid that has to have a similar weight.
 
The longer fuel inlet needle works against high rpm application's. The more mass will not go up and down to meter fuel but hang there. Seen it on dyno first hand with face above diaphragm cover with hole cut in it. Hi rpm it buldges up and sits there stuck wide open. Pouring raw fuel into carb. Than it finally closes and stays closed and now engine running lean constant because no fuel coming in. When you bring rpm down. Every thing works like normal. Go wide open or high rpm like long straight. Back to sticking inlet needle.
https://www.researchgate.net/figure...and-ethanol-fuel-properties-23_tbl1_325407074
Back when we built quarter scale cars. There was a guy who was a pro nitro racer. Alky was ok to use in the sprint and supermod classes. He ran alky and nitro and destroyed the field with it but he destroyed carbs after a few heats and had to mix fuel for each heat and main. Watching air density, temp, and humidity and mix as needed. So YES he was faster but to have to mix each time and the garbage can scattered with dead carbs to me was not worth it. The straight alky guys had to change jets on their Walbro carbs but that was easy to do if they needed too during day.
 
Last edited:
@HXRC good question, i believe @TODD Mentioned glow plugs for lightening the rig but to be honest I don't think these engines would survive anything higher than what we normally see.

Interesting read on the carb stacking, would be interesting to see if it would work. One thing I didn't see is the pulse port would need to be shared for both carbs and I would think you would need to drill straight through the rear carb to link the pulse port,not sure if that's possible yet.
 
Rep732 said:
@HXRC good question, i believe @TODD Mentioned glow plugs for lightening the rig but to be honest I don't think these engines would survive anything higher than what we normally see.

Interesting read on the carb stacking, would be interesting to see if it would work. One thing I didn't see is the pulse port would need to be shared for both carbs and I would think you would need to drill straight through the rear carb to link the pulse port,not sure if that's possible yet.
Click to expand...
you can add a puse line externally if you need to.
 
HXRC said:
Not trying to de-rail, but what's the RPM limit for these ignition systems? I'd think you could pull more RPMs from a glow plug.

On topic:
How about stacking carbs?
Click to expand...
Max rpm do not know 100% on, but we have customers at times running 22,000 to 22,500 rpm. Normal range for us is usually 18,500 up to 20, 000 rpm constant. Keep in mind though this is using the two piece Zenoah ignition setup. Cars with one piece I can not give answer on it. Sorry.
 
A little update to the meth thread.

So I just slapped a new piston in the engine and left the damaged cylinder alone, the result is the piston is damaged from the cylinder and the ring is seized in the ring land. The ring is actually still good with no scoring or gouging to that and the rest of the internals but the cylinder definitely got chewed up more. Atleast I gave it a try and it ran for about 5 minutes then just shut off, didn't even record it as it was just embarrassing how crappy it ran :LOL: 20230717_192415.jpg20230717_192425.jpg
 
@TODD I unfortunately mixed it as I would for gad at 32:1. this damage was from prior to when we talked about the oil. I ran it again with a damaged cylinder and a new zen piston just to see if it will hold up which not so much.
 
Not going too hold up either if you keep mixing it light on oil. Looks like there is some grooves in it? Are they deep or feel bad or is it just the aluminum that is stuck. Did you take the aluminum off last time you seized it?
 
Back
Top
✖
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks