turbo motor rebuild clarification

[5280Busa]

Well my motor should be finished by the weekend but I do have some questions regarding pistons, spacers, etc.

I was told that stock pistons are better than aftermarket...True or False? Why?

I was told that MTC pistons suck...why? Most of the AMA Prostar Funnybikes run MTC on the their 6-sec turbo bikes

I also read that even if I install forged turbo pistons at 10.5:1 compression that I STILL need a spacer...True or False? Why?

How can I test to make sure my injectors are working properly?

I am having my motor re-built by a local shop but I wanted to make sure I am clear on what is the best for a turbo Busa running 8-9 PSI on pump gas.

Thanks

-S

 

[Doc_Busa]

Turbo pistons have thicker domes than stock and are stronger in general, but, if you running low boost, you MAY not need them, if you do need them, you will know when you engine blows up.

Do a search at suzukihayabusa.org on the MTCs. In general, they are considered to be an inferior design to the J&E's. The MTCs have sharper edges, which can promote preignition problems. I intend to post some pics, hopefully tonight, and you will see for yourself where the MTC weak spots are. I do not think it is a question of MTCs in general, just their turbo busa pistons vs. J&Es.

It depends on the pistons. With the J&E's, the tops of the pistons are very thick, which is good for a turbo application, but you must use a spacer to drop the compression ratio down. Even if they say 10.5, it is 10.5 WITH the spacer. In case this does not have you boiling enough, you will also have to install adjustable cam sprockets. If you mechanic has not mentioned this, get a new mechanic.

The dyno will tell you if your injectors can handle you application. In fact, the reason my bike ate the last set of pistons was most likely due to the stock injectors not handling the flow (they were at 100% duty cycle at full boost). The injectors will only run at 100% duty cycle for seconds before they shut down, run lean, melt pistons, etc. HOWEVER, if you keep the boost down, this will not be a problem. I would not recommend running more than 8 lbs of boost on stock injectors. I am running the Honda S2000 injectors, and they tuned MUCH better, PLENTY of fuel to go around, BUT, I can tell it is a bit rich on the low end... the price you pay. You can also get a secondary fuel rail, which is a better solution.

Remember, the lbs of boost relates to the compression ratio. If you go with turbo pistons and a spacer, you may wish to bump up the boost. Your builder SHOULD know this stuff, if not, consider going elsewhere or it will get $$$ real quick. You may want to consider a heavy duty output shaft while you are at it...

Good luck and keep us up to date on your progress...

 

[justintime2]

I have a stupid Q. Why the F would you bother?

I have heard so many stories from turbo owners about how much time your bike is in the repair stable as opposed to riding that it sounds like a rediculous venture. Not trying to be a fly in your ointment, just don't understand why all the hassle and $$$. Get one of the ugly Boss Hoss's with a V-8 and built the crap out of it. I know it can't corner for poop and is ugly, but your turbo isn't being bought for the twisties.

 

[justintime2]

Well my motor should be finished by the weekend but I do have some questions regarding pistons, spacers, etc.

I was told that stock pistons are better than aftermarket...True or False? Why?

I was told that MTC pistons suck...why? Most of the AMA Prostar Funnybikes run MTC on the their 6-sec turbo bikes

I also read that even if I install forged turbo pistons at 10.5:1 compression that I STILL need a spacer...True or False? Why?

How can I test to make sure my injectors are working properly?

I am having my motor re-built by a local shop but I wanted to make sure I am clear on what is the best for a turbo Busa running 8-9 PSI on pump gas.

Thanks

-S

Also, if your motor is almost done these Q's may have come too late? Hope that any changes you may make can be accomodated.

 

[Uncle Bob]

I have a stupid Q. Why the F would you bother?

I have heard so many stories from turbo owners about how much time your bike is in the repair stable as opposed to riding that it sounds like a rediculous venture. Not trying to be a fly in your ointment, just don't understand why all the hassle and $$$. Get one of the ugly Boss Hoss's with a V-8 and built the crap out of it. I know it can't corner for poop and is ugly, but your turbo isn't being bought for the twisties.

spoken like someone that has never ridden a turbo'd busa

To understand someones madness, you must first try what they are smoking....

 

[Uncle Bob]

Well my motor should be finished by the weekend but I do have some questions regarding pistons, spacers, etc.

I was told that stock pistons are better than aftermarket...True or False? Why?

I was told that MTC pistons suck...why? Most of the AMA Prostar Funnybikes run MTC on the their 6-sec turbo bikes

I also read that even if I install forged turbo pistons at 10.5:1 compression that I STILL need a spacer...True or False? Why?

How can I test to make sure my injectors are working properly?

I am having my motor re-built by a local shop but I wanted to make sure I am clear on what is the best for a turbo Busa running 8-9 PSI on pump gas.

Thanks

-S

I can only speak in general terms, not your specific issues, but I would be surprised if you couldn't get a set of pistons to your specifications that don't need a spacer. Usually you call up the piston company and say "I need a set of turbo pistons that will put me at 9:1" and thats what they send you.

Not only are aftermarket pistons better because they have thicker domes, they usually have thicker lands too, to help prevent the lands from breaking under bad detonation, but as with thicker piston domes, this isn't REQUIRED, its more just a safety incase you detonate a little here and there. The much better answer is, don't detonate in the first place.

The biggest disadvantage to aftermarket pistons, especially turbo pistons, is that they are usually a lot heavier than stock pistons. But the advantages usually outweigh the disadvantages. I can't comment on MTC, but everyone usually has good comments about J&E....I have had bad dealings with Wiseco and would definitely not suggest them...but that was one time.....

Shimming up the base "works", but then you start throwing off your squish band, which I have been told can create its own detonation due to the turbulence dynamics getting thrown off, creating "dead spots" in the combustion chamber causing too much heat transfer to that section. I can't say I've personally experienced this yet, but if you're putting the money into it by buying new aftermarket pistons, I'd want the squish band to be optimal.

For the amount of boost you're talking, I personally wouldn't replace the pistons. Shim up the base a decent amount and leave it. If you're going for big numbers....then pistons are a good idea.

As for the injectors "working properly...?", are you refering to the spray patern, or quanity, or computer?