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TTR125 running e85 fuel?

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Anyone set their TTR125 up on e85 fuel? Trying to find a decent alternative to race only fuels for my 13:1 piston TTR125 (clone) with BBR cam and TM24 carb. Race fuels are too far away and very expensive, e85 might be right in town (need to verify) and of course about $20+ cheaper per weekend at the track (paved road racing).

 

If you guys are interested, here's the track with pictures of the brand new pavement, getting a little excited for the first weekend this year (delayed because of the paving and poor weather to finish the paving). http://ovrp.net

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Can't comment on e85 in a carb , but I would run meth if I were you

 

Even in my car (a 2012 mazdaspeed3) I have to clean out my fuel pump internals every 15-25k miles because I run a 60% 93oct and 40% e85 mix. I would imagine it will clog a small carb like that extremely easy. Not to mention e85 is hard on fuel lines and gaskets not specifically made for it.

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No, too hard to get and we might be regulated against methanol since it's hard to see when you have a fire. Really hoping pump gas is the answer to lack of supply.

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No, too hard to get and we might be regulated against methanol since it's hard to see when you have a fire. Really hoping pump gas is the answer to lack of supply.

I edited in a little for my reasoning on meth over corn

You can order bulk meth online also

 

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It can be done.  Jetting needs to be 30% richer over current jetting.  Make sure you get fuel line that can handle ethanol.  Also, get an ethanol stabilizer like Star-Tron to help slow down the fuel from causing corrosion and condensation problems.

 

Keep in mind any alcohol or methanol fuel will literally absorb humidity out of the air into the fuel system when sitting, causing major internal corrosion issues.  

 

Honestly, for your personal situation, it might be worth adding a couple extra base gaskets under the cylinder to reduce the cylinder pressure enough to run 91 oct pump gas.  

 

What is the cold cranking cylinder psi right now?  What is the duration and overlap of the cams?

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Let me start be saying that I talked to Chad at Sudco. He said people have done this (e85), but they had to machine (drill) the needle jet to get more flow in the part throttle regions. He also said they go through a lot of needle jets due to the electrolysis between the brass and stainless. Since the TM24 uses a "special" needle and probably a special needle jet, I may be done. The carb comes with a Q0 needle jet, I have a P8 jet (next leaner) and may try to track down a Q8 jet and see if it fits (next richer and suggested on the Mikuni OZ site). Seems there are lots of parts that fit these TM24 carbs that are available in other parts of the world, but not in the USA, don't know why. Now the needle itself is an issue, there are no others with direct fit due to the short throw. There are a few others that might work, and I need to go back to my notes and maybe buy a couple for testing.

 

The Cam is the BBR performance grind for the TTR125, no real information on the overlap. I do know that when I kick it over a single time, the compression gauge reads a very low amount (like 60-70psi). If I kick it a bunch of times I got up to around 240psi (rings still covered with assembly lube or wet, no carb attached), each kick improved the pressure. Before the cam swap the first kick was over 100 and by the third kick the pressure topped out at like 130-140psi (9:1 and stock cam). Not sure if any of this helps to determine the dynamic compression. If (big if) I could determine the dynamic compression (taking into account the loss from overlap), I might find that I could run a much lower octane fuel. I started reading about that last night, but we don't have any real concrete facts about the BBR cam. I would need to degree it and measure it to figure out the specs. All I know is that there is more (or now some) overlap between exhaust closing and intake opening because I see it in the valves, hear it in the air pumping, and finally see it on the compression gauge. I have tried to contact BBR about the cam, but they will not reply about the specs., even though it means a lot in the tuning game!

 

I would love to be able to get this down to 93 or 94 pump gas, so much easier to get. Down to 91 no alcohol would be even better but a big risk without knowing what's going on.

 

And finally for the big issue... At 90 degrees F, I'm at the second to smallest pilot jet and I could see needing the smallest jet and maybe running into a rich condition. Background is that when you go through and dimple the intake manifold, intake port, and intake valve, the mixture stays mixed and flows a lot better. This causes a rich condition unless you jet down and I'm finding that you need to jet WAY down. I did this with the stock carb and had to switch to 93 gas to thin it out with the alcohol, and still was running way rich. Added a bunch of Seafoam to thin even more for the one practice where this occurred at the end of last season (and it was a cold day). I was expecting that with the piston and cam upgrades I might be in a better section of the TM24 carb, but finding myself setting it with very small jets to try and get where I need to be. Tuning with Innovate MXT-L wideband o2 sensor. I did some work last night and find that the numbers I thought I needed were wrong, so I need to go a little richer due to the added alcohol in the Power Mist UL RFG (approximately 20% but no data sheet so just a guess). Looking for an AFR between 11.5 and 12 to 1 for good power and I'm at about 12.5:1 at idle right now with a slight hesitation off idle. When it was slightly more rich the throttle jumps off idle with no hesitation and I get a good feeling about this carb in the long run.

 

If there is more detail I can provide to help determine the dynamic compression, please let me know. Getting to a common fuel would be so very nice, even though I will probably need the alcohol to thin it out so I don't run out of jets.

 

Eventually everything I learn will go on my website to help other people, especially since this KAYO has limited knowledge out on the web. http://minigp-racing.com The info about the intake dimples is in the Skunk Works area, which requires a free account to read. Don't want to give the extra special sauce to everyone, it's all from the web just distilled down and pictures for easy consumption. The bulk was from a Hotrod magazine article backed up by several other posts and articles, and then backed up buy a builder on a Buell forum who does this on all his builds (personal and customers). In essence the rough CNC surface cutting does the same thing, it's not about bigger ports, just making sure the "fluid" flows through well and around the corners well. Same principle as vortex generators to smooth out flow over a surface feature. Makes more power? Not sure. Saves fuel? Certainly uses smaller jets to run the same so it must save fuel. In theory (and some practice) it makes small amounts of power, and on these little engines every little bit counts a lot.

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Can I simply measure the amount of cylinder the piston sweeps after the intake valve closes to get that part of my DCR equation? I did send an email to BBR to see if they will help me, but I'm not expecting too much there, even though you can see in this picture that I am using a BBR cam (you can see the BR stamped in the cam)

DSCF0420.JPG

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Well, I have to change something... BBR did get right back to me. Unfortunately a lot of the cam info has been lost in the last 17 years. What they have left is as follows:

 

Quote

 Intake:

        Lift:                .224" 

        Duration:    208.8

 

    Exhaust:

        Lift:                .221"

        Duration:    205.2

[/quote]

 

Not sure how this much overlap compares, but fair to say it is more than the stock cam based on my compression testing. What we don't have is the lobe centers, so not certain about lobe timing and how long the intake stays open after BDC. It must be some because it doesn't kick any harder than stock, and might even be easier to kick now. This suggests that the dynamic compression is lower than the stock cam, but I'm not certain.

Edited by Greg_E

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