GT750 Frame Weight Reduction

water cooled · Post by **water cooled** » Sun Nov 08, 2009 12:36 pm

[/quote]Didn't you get a moly frame?[quote]

Tom, I do have the lighter frame still. Steve Hamilton found it for me and it shouldnt take too much to get the GT engine to fit.

The real issue with using the moly frame is that it will force me into a quicker sub-class. If I stay in "Modified" I need to use the stock frame and meet or exceed 10.0 seconds for my displacement. So my engine is lagging behind. Until I can beat 10 sec with the stock frame, the moly frame will actually hurt my chances during Qualifying Rounds.

The frame change might save 1/10th or so but Im still 1.4 seconds out from where I should be.

We'll see how close I get next spring.

Suzukidave · Post by **Suzukidave** » Mon Nov 09, 2009 5:20 am

water cooled wrote:
The frame change might save 1/10th or so but Im still 1.4 seconds out from where I should be.

Kevin for that making the bike lighter may help a bit but it looks like you need more HP .. i need to send you those 40mm flat slides i have sitting around

.

water cooled · Post by **water cooled** » Mon Nov 09, 2009 6:00 am

Dave, those look great. I bought some power jets for the 38's and need to work out how to get the one on the right to clear the clutch hub. Im not sure milling the block for a steeper angle is an option for me. No doubt the 40 flat sides would be an improvement... I forgot you had those. I'll have to think about that one.

I think my exhaust is the first item to get past...its dropping off just over 8k.

Tom Garcia · Post by **Tom Garcia** » Mon Nov 09, 2009 6:50 am

water cooled wrote:
I think my exhaust is the first item to get past...its dropping off just over 8k.

Know a decent laser or water jet shop in our area to cut cones??? I've started looking....

water cooled · Post by **water cooled** » Mon Nov 09, 2009 7:46 am

The only one I know locally is Litchfield Welding but his machine cuts large pieces. I dont know how small he could do but it may be worth checking into.

Its a one man shop specializing in all forms of welding but he also performs a lot of fabrication work too. He doesnt turn away any small jobs. Its located on the rotary off Rt18 and 82 west of Medina. The owner is Steve.

David Derrick is another source and he is located in Michigan (D&D Chassis). You may have seen him post on the Kaw board welding up some chambers he was making for one of the racers. I have his number if you need it or you can contact him through the board.

Besides Medina Performance Machine Shop, do you know a good machinist that can cut my GT250 forks and springs? Medina Performance Machine is good but they can be expensive.

tz375 · Post by **tz375** » Mon Nov 09, 2009 7:50 am

Kevin,

Did you get those exhaust dimensions for me yet?

water cooled · Post by **water cooled** » Mon Nov 09, 2009 8:37 am

I will take care of that today...sorry for the delay.

Tom Garcia · Post by **Tom Garcia** » Mon Nov 09, 2009 8:55 am

water cooled wrote: Besides Medina Performance Machine Shop, do you know a good machinist that can cut my GT250 forks and springs? Medina Performance Machine is good but they can be expensive.

If they just need to be shortened and cut with an internal groove we can probably do that on the lathe at my buddy's place... IE: FREE

Suzukidave · Post by **Suzukidave** » Mon Nov 09, 2009 5:21 pm

What i have read its the last cone angle that has the greatest effect on where the pipe cuts off but even the down pipe on the Jemco's are pretty basic as it should be tapered almost to several inches to the cylinder for best return . You may be able to get away with a chamber rebuild changing the last cone to extend the over rev ?

tz375 · Post by **tz375** » Mon Nov 09, 2009 5:34 pm

Dave,

That would be nice if it worked out that way.

When I have the JEMCO data, I'll push it through a couple of bits of software I have here, to simulate the power curve with existing ports, then I'll input revised port timings that I think will work and then I'll start to modify the pipe designs to see if I can get it the right side of Kevin's target.

If it were me, I'd go straight for the record breaking H2's and try to top those numbers, but that may be slightly ambitious

Targets have to be more realistic than that, but we need to aim high just to end up where we need to be.

I may have to borrow the pipes from the SRAD project. Just let me know which nights you work late, and I'll arrange for them to be "collected"

Suzukidave · Post by **Suzukidave** » Mon Nov 09, 2009 5:52 pm

tz375 wrote:Dave,
That would be nice if it worked out that way.

I might have been making things a bit too simple huh

tz375 · Post by **tz375** » Mon Nov 09, 2009 8:53 pm

Simply shortening the pipe will raise the tuned speed but as the motor runs hotter and harder, the gas temp tends to rise and that means the pipe is too long again....

You are correct though that a shallow angle on that convergent nozzle tends to result in more over rev but less power. Sharper angle tends to create a stronger stuffing wave, higher peak power and shorter rev range over which it works.

I suspect that if we were to raise ports and overall power, the motor would respond and could use larger cones and a fully tapered header, along with a shorter length.

I'll run some sims with higher BMEP and bigger ports and match the pipes using either Bimotion, Blair or MOTA (ITW) pipe designs. All use the same formulae and all three give different suggestions. I'll take all three and start running additional sims and see what the software thinks that the motor might like.

water cooled · Post by **water cooled** » Tue Nov 10, 2009 6:21 am

Richard,

I have the aluminum shim from Cometics so the porting will go up 3.18mm from the numbers you have. The block will be decked accordingly.

Rough estimates indicate that 95 RWHp will be required to get the bike to run mid-10's at current weight.

tz375 · Post by **tz375** » Tue Nov 10, 2009 8:37 am

We can do better than that.

tz375 · Post by **tz375** » Wed Nov 11, 2009 10:53 pm

Of course we could always try to beat the fastest H2. What does it make? 245hp?

That might be a bit of a reach

I'd like to know how they get those sorts of numbers. 100 is hard enough to get some of those boys are well the other side of that number. There isn't enough cylinder wall for the port area that would need.

Are they all running race gas or do any of them use Methanol or Nitro (or nitrous)

GT750 Frame Weight Reduction

Moly Frame

Re: Moly Frame