MillerModSaws and the PS-7910

[KG441c]

With the tight crankcase volume would raising the upper transfers higher than 129 be beneficial or not?

 

[MillerModSaws]

With the tight crankcase volume would raising the upper transfers higher than 129 be beneficial or not?

Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.

 

[Hedgerow]

Unless it runs out of go go. On the second saw I will most likely go 2 degrees higher so it will have 25° blowdown. If it goes backwards I will raise the exhaust to 100 to get my blowdown back.

Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!

 

[MillerModSaws]

Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!

I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.

 

[Hedgerow]

I agree. If u notice I havnt faired to far off a 7900s numbers. This saw may be a real good canidate for the epoxied intake due to its need for cranckcase pressure. Also Andyshine has give me a couple helpful warnings on this saw.

Andy is as crazy as a shithouse rat...
Gotta watch that guy...

 

[Hedgerow]

 

[MillerModSaws]

Andy is as crazy as a shithouse rat...
Gotta watch that guy...

I'm sure he'll be along to defend that statement. Lmao. But by the end of this thread hopefully we have an awesome recipe going for this saw.

 

[drf255]

Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?

My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?

 

[Hedgerow]

Why does this particular saw require so much more blowdown than another similarly designed quad port like a Husky?

My blowdown on a Stihl is 16-18*. What's the reason for the vast difference?

Some say Stihl transfers are a bit lazy and require more time open..
A head start you could say..
But that varies from model to model..

 

[MillerModSaws]

Some say Stihl transfers are a bit lazy and require more time open..
A head start you could say..
But that varies from model to model..

An example of model to model. I set the ms441 at 25° blowdown.

 

[blsnelling]

I set the ms441 at 25° blowdown.

That's a lot.

 

[KG441c]

That's a lot.

Would u explain Brad? Thanks

 

[ELECT6845]

An example of model to model. I set the ms441 at 25° blowdown.

I have been leaving more blowdown in the new model Stihls along with more intake. They seem to like it and make alittle more torque. Guess it all comes down to what a guy prefers.

 

[MillerModSaws]

That's a lot.

What do u use. I take .050 off squish band. 100/125/78 iirc. But that seems to be the best combo I've found so far. I did try 23 blowdown and maybe it was the combo I tried but it like 25 blowdown better.

 

[blsnelling]

I don't want to quote any numbers until I'm home to check my records.

 

[mdavlee]

Blowdown and degrees of crank case compression are important on these saws.. But so much is still unknown on them... Even saw builders who are well versed are confounded by them.. They run very well in stock form, and are very tough to improve on..

Those folks at Dolmar sure didn't leave us any low hanging fruit!!

Your red one has 30° of blowdown. if I remember right it has 45° of crankcase compression.

 

[blsnelling]

In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?

 

[old-cat]

Blowdown and degrees of crank case compression are important on these saws..

Another saw with small crankcase volume is the 357xp and the oem timing is ex. 106, transfer 118, intake 73
Thats 12 degrees blowdown!????????

 

[komatsuvarna]

In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?

I agree, it doesn't.

The transfers will still be too high..

 

[MillerModSaws]

In my limited experience with these, they need LOTS of blowdown. And, simply raising the exhaust up to remedy transfers that were raised too much, doesn't work that well.

What's the stock exhaust port timing on a 7900?

I'll agree to however. In building these I want to try a 100 degree exhaust height. See how that works. So I would be at 100/127 if I tried that. Stock exhaust height from what I've read is 105 on the 7900 with 27 blowdown.