dasa compression ?

[Just4Fun]

I have a used ss 850
89mm bore
44cc domes
What comp should I be at?

Anything special to comp testing a powervalve engine ?

Thanks
Matt

 

[Jetfiend]

What size domes are you running?

 

[DAG]

Debate is do you hold PV's open or let them float. You will get different readings

 

[Just4Fun]

44cc domes

 

[Jetfiend]

My 42cc domes put my 89mm right at 190 with the PV closed.

 

[Just4Fun]

My 42cc domes put my 89mm right at 190 with the PV closed.

Thanks I'm gonna do a comp test and post the findings to see what you guys think.

 

[Just4Fun]

View attachment 301541

 

[Just4Fun]

 

[Just4Fun]

150 and 155ish is this low pulled head and pistons and cylinder walls look good. I emailed dasa a while ago they said for every 2cc is about 15 psi That means I should be 175ish which I get when I pour oil in the cylinders.
Should I just order smaller domes?

 

[jo5hi3]

Is the engine warm?

 

[Harbor]

What's your elivation ? Can you get a second gauge to verify the ready as well ?

 

[fast superjet chase]

What altitude are you at

 

[fast superjet chase]

You lose about 7psi per 1000'

 

[Just4Fun]

What's your elivation ? Can you get a second gauge to verify the ready as well ?

2000'
Verified on a second gauge
Talked to chuck at Cpt
44 domes and 89mm bore
Will put out about 150psi give or take a little

 

[jo5hi3]

I think I ran 46cc domes on my dasa 1000.

 

[Just4Fun]

I m gonna order some 42s and see what comp i end up with, lookin for around 180 190 .. I got this motor used and it was advertised as a 210 psi setup. Lol

 

[Nuklear6]

I think I ran 46cc domes on my dasa 1000.

Displacement effects compression ratio

Static compression ratio:
850cc with 44cc domes= 9.5:1
1000cc with 46cc domes= 10.5:1

Dynamic (trapped compression ratio (with PV open/approx exhaust port opening @ 84ish deg atdc)

850cc with 44cc domes= 5.9:1 (perfect world compression test about 145-155 psi cranking compression)
1000cc with 46cc domes= 6.5:1 (perfect world compression test about 160-170 psi cranking compression)

Hope this helps understanding

 

[badvinny]

If you don't know for sure how many hours on it you could pull the cyl's and inspect your new used motor that was supposed to have200 but has 150. Then order your domes and anything else you may need.

 

[jo5hi3]

Displacement effects compression ratio

Static compression ratio:
850cc with 44cc domes= 9.5:1
1000cc with 46cc domes= 10.5:1

Dynamic (trapped compression ratio (with PV open/approx exhaust port opening @ 84ish deg atdc)

850cc with 44cc domes= 5.9:1 (perfect world compression test about 145-155 psi cranking compression)
1000cc with 46cc domes= 6.5:1 (perfect world compression test about 160-170 psi cranking compression)

Hope this helps understanding

I'm well aware of how to calculate the compression ratio. Everyone wants to know what it reads on a gauge, the only thing a gauge is used for is state of health..... Bigger cc motor with the same cc domes will net a higher compression ratio.

 

[Nuklear6]

I'm well aware of how to calculate the compression ratio. Everyone wants to know what it reads on a gauge, the only thing a gauge is used for is state of health..... Bigger cc motor with the same cc domes will net a higher compression ratio.

My comment wasn't meant to insult you in any way. It was to clarify further from your post. So people who browse this now and later through the search function have an understanding of why they would need to run different domes on same brand cylinder with different displacements. Again I don't know everyone's knowledge or ability, I was just trying to clarify.