Engine Misfire - UPDATE - Over Rev

[Martens199]

Yes they will gain HP as the motor breaks in. When I pushed mine to 13#'s of boost the motor had been rebuilt and we tuned the clutch on the track dyno at Ulmer's. After 400 miles the engine was making so much more HP that the clutching was at 9000 rpms on 9 #'s and would over rev badly at 13. Had to add a lot of weight. The primary spring will not gain you much you can try going to 3-3 on the secondary though. That has settled mine down as it got more power till I could add weight.

Yeah it's was originally set up at 3-1 and I did try setting it to 3-3 which did make it slightly better but still on the limiter off the hop. I have the 96 gram MCX weights with a green green green spring currently, the weights only have one hole in them for rivots. MCX is not sure what to tell me to do since I'm the first with this problem it seems. Would I add more weight to the mcx wieghts?

 

[Yamadog]

it depends on the starting weight of the arms but I know I had a hauck clutch kit in mine when it was first built and when we upped the HP it could not get enough weight in the arms. Allen set it up on the dyno and his kit would not allow enough weight. He switched them out to I cannot remember who's but I am running over 100 grams with less hp than you and still bang it when the track breaks free.

In this vid the first launch is at 9 #'s of boost and it is fine but 2nd run at 13#'s still hits the limiter on takeoff. Which you would not think it would be building that much more boost at launch but it does. These quick spool waste gates are really fast. Allen has the clutching so aggressive that when it hits you know it.

 

[Martens199]

Yup mine is doing the same thing, with a backfire sometimes when it hits the limiter. I will attach the picture of the weights I'm running. Just need to know if this is a spot for some rivots weights or just a design of the weight arm.

 

[Yamadog]

You could try it as long as you can secure them. It cannot hurt at least for a trial. The backfire is your un-burnt fuel dumped in the cylinders when it cuts out your exhaust or valves are hot enough to ignite it as it exits through the exhaust. When you start getting over 250 hp the clutching becomes very tricky to get the balance on launch and hold the revs at WOT. Do you have a PC5 or gems controller type of fueling controller on that turbo. You could go PC5 and increase the rev limiter that is what I am doing on both of mine so that it is not quite as touchy on the clutching curve.

 

[Martens199]

Its just the none adjustable MCX box controller, unless I had a computer hook up.

 

[Yamadog]

Gotcha, That will only change your fuel map, you could do EVO re-flash to raise rev limiter but adding weight is your best and cheapest way.

 

[Martens199]

Gotcha, That will only change your fuel map, you could do EVO re-flash to raise rev limiter but adding weight is your best and cheapest way.

What weight would you suggest adding to those arms?
My current set up is MCX 96 gram weights g,g,g primary spring, 14.5mm rollers. Stock secondary set up. Pink spring 41 helix and a OSP adjuster running a 8DN belt. I tried going back to a 8JP belt but then I was on the limiter steady.

 

[turbotundra]

What weight would you suggest adding to those arms?
My current set up is MCX 96 gram weights g,g,g primary spring, 14.5mm rollers. Stock secondary set up. Pink spring 41 helix and a OSP adjuster running a 8DN belt. I tried going back to a 8JP belt but then I was on the limiter steady.

Try running a blue-white-blue primary spring, 14.5 rollers, purple EPI cat secondary spring (1-0) and a 47* or 51* helix.

 

[Armani]

You could try it as long as you can secure them. It cannot hurt at least for a trial. The backfire is your un-burnt fuel dumped in the cylinders when it cuts out your exhaust or valves are hot enough to ignite it as it exits through the exhaust. When you start getting over 250 hp the clutching becomes very tricky to get the balance on launch and hold the revs at WOT. Do you have a PC5 or gems controller type of fueling controller on that turbo. You could go PC5 and increase the rev limiter that is what I am doing on both of mine so that it is not quite as touchy on the clutching curve.

I have a Viper MTX 270 MCX, and PC5 /w ign module, got the REV ex code, but still hitting rev limit at 9350rpm.
Is there anything i could have done wrong? Is your`s unstable, working sometimes and hitting rev limit another time?
Will hurt my engine, if clutching to 9800rpm but risk hitting the rev at 9350

 

[Yamadog]

Yes mine makes more hp in certain conditions temp, altitude and humidity still play a big factor. Even though I am clutched for 13#'s I can still hit it on wot runs at 9#'s. Both you guys are running MTN machines so your gearing is much lower and plays a part in that also. Hitting the limiter will not hurt it just takes away power.

Armani if your running pc5 and clutched for 9800 rpms and hitting the rev limiter it did not move your rev limiter unless you meant to say 8800 rpms. 9800 seems awful high and bad for the clutch.

Primary springs, helixes, arm weights, gearing and drivers all play into what is happening and you can chase it several ways and get more screwed up then before. I would start by adding a few grams to the arms and see what kind of results you get. Then spend money on more parts if a no go. Even where the weight is in the arm will cause it to hit faster and over rev on launch and then come back to you at the top end. I used to run Heel clicker II because you could load those in 3 places in the arm and then on the rotating weight it took a bit to get dialed but when drag racing you could get an apex to snap to 10,900 rpms and stay there through out the entire run.

 

[Yamadog]

What weight would you suggest adding to those arms?
My current set up is MCX 96 gram weights g,g,g primary spring, 14.5mm rollers. Stock secondary set up. Pink spring 41 helix and a OSP adjuster running a 8DN belt. I tried going back to a 8JP belt but then I was on the limiter steady.

I don't know but I would think if you get too much you wont pull over 8600 rpms and then back the weight down from there. I would try to get another 5 in it if possible.

 

[Yamadog]

Here is the Hell clickers 2 speed arms you could really load these. I have a couple sets from the old days I may build a spare clutch for my 15 and give them a try if I ever get them back from the shop. you can run them with as many washers as you want as long as they clear the towers.

 

[Martens199]

Try running a blue-white-blue primary spring, 14.5 rollers, purple EPI cat secondary spring (1-0) and a 47* or 51* helix.

I have a blue pink blue spring coming, is the blue white blue even softer? BTW is there a yamaha chart somewhere? I want to go with a bigger helix too but I have been reading that adding weight to the primary is always better. (and cheaper lol). What is the idea behind the Cat spring?

 

[Martens199]

I don't know but I would think if you get too much you wont pull over 8600 rpms and then back the weight down from there. I would try to get another 5 in it if possible.

Ok Yeah i will try getting it up to 100grams, easy enough to drill out if it doesn't help

 

[Yamadog]

Well its hard to envision but if the secondary spring is too soft and the primary clutch starts to shift out the secondary opens too easy allowing the primary to overdrive the belt if you get my meaning. So it results in lighter tension and slippage will cause you to over rev.