PS-7900 vs PS-7910

[FATGUY]

Hi Nik!
























Pacer lover!

Baaaah Humbug!!!!!!!!!!!! That limited coil in and of itself is enough to ruin that claim.

you just have no taste, never have...

 

[blsnelling]

you just have no taste, never have...

You're right. I have no taste for Pacer chainsaws:msp_biggrin:

 

[FATGUY]

You're right. I have no taste for Pacer chainsaws:msp_biggrin:

but you do have an affinity for riding on the back of Harley's? :jester:

 

[166]

I dug out a NOS PS-7300 Orange Top that I had new in a box for a comparison of the three color schemes for this saw.

Late Model PS-7900

The New PS-7910

PS-7910 Carburetor

PS-7910 SLR Muffler

 

[Rudolf73]

I dug out a NOS PS-7300 Orange Top that I had new in a box for a comparison of the three color schemes for this saw.

The New PS-7910

Ooooo it's got a matte black finish! :msp_wub:

 

[blsnelling]

What is SLR?

 

[benp]

What is SLR?

Scavenging Losses Rejection.

This is from the flyer that E & E posted a while back about the 2012 models.

 

[SkippyKtm]

Seems like there would be some loss of power with the SLR system due to an overly restrictive exhaust, No?:msp_confused:

 

[Miles86]

Hi-

OK, so if I am understanding this right, the SLR chamber in the muffler is acting as a sonic resonator, or like an expansion chamber on a 2 stroke motocross bike?

Is this savenging loss stopped by sonic wave tuning or by physical backpressure? Thanks for the great photos.

 

[tdi-rick]

My understanding of the new muffler is that it's a controlled bleed.

It's using backpressure from the inner chamber to reduce the scavenging losses. This then bleeds into the main body of the muffler.

It'll be interesting to see what differences there are in port timing and port sizing between the new and old jugs too.

 

[SkippyKtm]

My understanding of the new muffler is that it's a controlled bleed.

It's using backpressure from the inner chamber to reduce the scavenging losses. This then bleeds into the main body of the muffler.

It'll be interesting to see what differences there are in port timing and port sizing between the new and old jugs too.

That's my take on it too, it reminds me of a Husky 266 I bought on CL with a plugged exhaust where the muffler itself was behaving somewhat like a primitive Dolmar chamber, except with less bleed. It would start just fine then run for about 5 seconds and quit. Then you could restart it right away once the pressure bled off and repeat the same process. I'm not saying the 7910 would run exactly that way, but I'm guessing that there is something lost there.
I hope I'm wrong, but time will tell if there is some loss in power -there's no free lunch so to speak.:msp_mellow:

 

[w8ye]

As far as the so called bleed rates or the tuning of the muffler chamber goes, I could see it being more effective, EPA wise, at certain rpm's?

 

[SawTroll]

You better not let Niko read that the 7910 doesn't weigh more. He was just waving that around in another thread moments ago.

Is there any chance the new coil is unlimited??? Nahh, I didn't think so...that would be too easy!

That is specs, and according to those the 7910 is heavier, and has .3 kW less power - but specs are specs....:msp_sneaky:

The 7910 specs are 14.7 lbs/6.7 kg and 4.3 kW/5.9 hp - the 7900 specs were about a pound less (6.3 kg) and 4.6 kW/6.3 hp.

It was well known that the weight spec of the 7900 was "optimistic", but it hardly was known that it weighted as much as Scott found.....:msp_confused:

A rev limiter at 12,800 sound really scary, what's the reason for that? :msp_scared:

Btw, my brother is very happy with his 7900 (a new Euro one) so far, except that the potential for porting is somewhat limited.....

 

[Tim Carroll]

Well the NEW PS-7910 are selling, and anyone that has bought them or tried them has been HAPPY. As far as NET Weight for Power Head Only as comes in the box here are the results...........

Stock Dry New PS-7900 per our digital UPS Legal scales 14.8 pounds
Stock Dry New PS-7910 per our digital UPS Legal scales 14.8 pounds


Hmmmm same weight, brattier exhaust note, NO CAT, Adjustable Carburator, 15% better on fuel, cleaner running to keep the EPA happy whats not to like??
as far as gross horsepower well I dont have a dyno But in side by side comparison cutting real Logs burring a 24" bar in hardwood 7900 vs 7910 the power and torque are very close!
The EPA Legal saw is still VERY EASY to Service, and do repairs to no major redesign to the saw..., it does have a SLR Muffler, new Cylinder with top side deco, the new lightweight piston same as late model PS-7900's New crank, new coil and a different flywheel. The carb has adjustment screws and a vent hose off the metering pump cover. So again Whats not to Like I ask?????

Both above models are less weight than the CAT equipped PS-6400



Scott

Thanks for posting your findings Scott, I was curious about how the new saws compared myself. I am glad Dolmar has a viable replacement for the 7300 and 7900. I was worried they would not get it figured out.

 

[166]

That is specs, and according to those the 7910 is heavier, and has .3 kW less power - but specs are specs....:msp_sneaky:

The 7910 specs are 14.7 lbs/6.7 kg and 4.3 kW/5.9 hp - the 7900 specs were about a pound less (6.3 kg) and 4.6 kW/6.3 hp.

It was well known that the weight spec of the 7900 was "optimistic", but it hardly was known that it weighted as much as Scott found.....:msp_confused:

A rev limiter at 12,800 sound really scary, what's the reason for that? :msp_scared:

Btw, my brother is very happy with his 7900 (a new Euro one) so far, except that the potential for porting is somewhat limited.....

13.6 Pounds Original PS-7900 with Euro Small Spike Bar and no clutch cover
13.8 Pounds Original PS-7900 with large US Spike Bar and no clutch cover
14.6 Pounds Original PS-7900 with US Spike bars and clutch cover
14.8 Pounds Late model PS-7900 with US Spikes and clutch cover with minor changes and upgrades in the saw
14.8 Pounds New PS-7910 with US Spikes and clutch cover

So in real world numbers this saw has gained .2 lbs in the last 10 years.

 

[Hedgerow]

Baaaah Humbug!!!!!!!!!!!! That limited coil in and of itself is enough to ruin that claim.

Where's that blasted DISLIKE button!!???

 

[SawTroll]

13.6 Pounds Original PS-7900 with Euro Small Spike Bar and no clutch cover
13.8 Pounds Original PS-7900 with large US Spike Bar and no clutch cover
14.6 Pounds Original PS-7900 with US Spike bars and clutch cover
14.8 Pounds Late model PS-7900 with US Spikes and clutch cover with minor changes and upgrades in the saw
14.8 Pounds New PS-7910 with US Spikes and clutch cover

So in real world numbers this saw has gained .2 lbs in the last 10 years.

So the 7900 specs were without the clutch cover - that's quite disturbing.......:msp_confused:

 

[redoakneck]

So the 7900 specs were without the clutch cover - that's quite disturbing.......:msp_confused:

Yes, Yes it is. It is a real challenge to keep the chain tight on these dollys as the tensioner is in the cover, and when the cover isn't on I have to hold the bar out and tight when I cut, and I am running out of fingers!!! Even my friends won't hold the bar when I cut, ya just can't find good help these daze.

 

[SawTroll]

Yes, Yes it is. It is a real challenge to keep the chain tight on these dollys as the tensioner is in the cover, and when the cover isn't on I have to hold the bar out and tight when I cut, and I am running out of fingers!!! Even my friends won't hold the bar when I cut, ya just can't find good help these daze.

 

[tdi-rick]

So the 7900 specs were without the clutch cover - that's quite disturbing.......:msp_confused:

I thought I'd read on here quite a while ago (and I thought you might have mentioned it) that's how some of the manufacturers presented their 'weights' in the past ?