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baldwin
Joined: 02 Nov 2002
Posts: 113
Location: The Hague, The Netherlands
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 Posted: Wed May 02, 2007 2:41 am Post subject: |
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Nice to see another "933" project!
The difference between your setup and mine is that I left the head stock, and went with custom 11:1 pistons. Also, I don't use the stock cam anymore.
Can't give you any hp numbers yet, because the engine is pinging at high rpms/load, probably because the mixture starts to lean out. Don't know if it's a vacuum leak, fuel system not working properly, or fuel system just not being able to cope with the 931 head + wilder cam. WbO2 is on its way.
You should be able to use NA injectors in the 931 head, just put in the plastic inserts that go with the NA ones. Mmm...or maybe I should use the 931 injectors for more fuel...
Anyway, I hope the NA distributor fixes your problems!
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'98 Volvo 940 LPT Estate |
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Tigger937
Joined: 11 Apr 2004
Posts: 919
Location: PCA Milwaukee Region
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| Posted: Mon May 07, 2007 1:46 am Post subject: |
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| baldwin wrote: | | Mmm...or maybe I should use the 931 injectors for more fuel... |
I believe the only difference between the NA & 931 injectors is the style of mounting. 931 injectors are threaded whereas NA are push fit. Porsche went with the threaded style to provide a better seal for the boosted motors.
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1981 931 (Concours)
1982 931 (Daily Driver)
"Think outside the box" |
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baldwin
Joined: 02 Nov 2002
Posts: 113
Location: The Hague, The Netherlands
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| Posted: Mon May 07, 2007 4:59 am Post subject: |
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| Tigger937 wrote: | | I believe the only difference between the NA & 931 injectors is the style of mounting. 931 injectors are threaded whereas NA are push fit. Porsche went with the threaded style to provide a better seal for the boosted motors. |
Yeah, that's what I thought.
For now, I assume the NA stock fuel system is adequate for the modifications I did, so I focus on vacuum leaks/faults in the fuel system first.
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924 parts, http://verkopers.marktplaats.nl/10266983
'98 Volvo 940 LPT Estate |
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brit2514
Joined: 21 Feb 2007
Posts: 18
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| Posted: Fri May 11, 2007 3:37 am Post subject: |
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i have finally got the car revving and timed correctly
used the new dizzy and also realised that the haynes manual has been lying to me
it says that the engine rotates counterclockwise when it clearly does not!
still got a problem with lack of power though
the car just has not got any grunt i have played around with the dizzy and the screw on the tb and can't get it to go properly
it just seems to slow
any ideas |
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Fri May 11, 2007 4:14 am Post subject: |
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| brit2514 wrote: | | still got a problem with lack of power though |
when you do a compression test, what are the numbers?
| brit2514 wrote: | | it just seems to slow |
Do you have a wideband oxygen sensor laying around you can give us numbers on at various rpm's n'such?
Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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brit2514
Joined: 21 Feb 2007
Posts: 18
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| Posted: Fri May 11, 2007 4:36 am Post subject: |
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compression test will be done tomorrow
what is a wide band oxygen sensor? |
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npjester
Joined: 24 Jan 2006
Posts: 31
Location: Baltimore Maryland
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| Posted: Fri May 11, 2007 4:51 am Post subject: |
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| brit2514 wrote: | | what is a wide band oxygen sensor? |
a wide band O2 sensor allows you to accurately measure your air/fuel ratio where as a normal O2 sensor is good for...nothing... j/k normal O2 sensors just gives lean or rich. where as the wideband gives everything inbetween.
please correct me if i am wrong 
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1981 931
1982 931
2003 MINI Cooper |
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Fri May 11, 2007 5:05 am Post subject: |
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pretty much.
A wideband oxygen sensor will show us if your car is running the correct AFR for max power at various rpm's.
Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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Lizard
Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada
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| Posted: Fri May 11, 2007 9:30 am Post subject: |
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| Tigger937 wrote: | | baldwin wrote: | | Mmm...or maybe I should use the 931 injectors for more fuel... |
I believe the only difference between the NA & 931 injectors is the style of mounting. 931 injectors are threaded whereas NA are push fit. Porsche went with the threaded style to provide a better seal for the boosted motors. |
thats funny I always thought they were different so if the wastegate failed there was no chance of the boost blowing the spraying injectors into atmo.
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3 928s, |
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Tigger937
Joined: 11 Apr 2004
Posts: 919
Location: PCA Milwaukee Region
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| Posted: Fri May 11, 2007 9:43 am Post subject: |
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| Lizard wrote: | | Tigger937 wrote: | | baldwin wrote: | | Mmm...or maybe I should use the 931 injectors for more fuel... |
I believe the only difference between the NA & 931 injectors is the style of mounting. 931 injectors are threaded whereas NA are push fit. Porsche went with the threaded style to provide a better seal for the boosted motors. |
thats funny I always thought they were different so if the wastegate failed there was no chance of the boost blowing the spraying injectors into atmo. |
But what a ride it would be! 
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1981 931 (Concours)
1982 931 (Daily Driver)
"Think outside the box" |
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Lizard
Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada
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| Posted: Fri May 11, 2007 9:46 am Post subject: |
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yes esp after the atomized fuel was ignited by the red hot exhaust manifold.
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3 928s, |
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RC
Joined: 25 Mar 2007
Posts: 2637
Location: Australia
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| Posted: Fri May 11, 2007 1:02 pm Post subject: |
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| Quote: | The volumes must be measured whilst the engine is being assembled.
CR= total cylinder volume(BDC) + combustion chamber volume /combustion chamber volume.
With piston at TDC apply thin coat of grease around piston circumfrence to seal rings to bore. Do same to piece of acrylic with countersunk 6mm hole in centre (CSK up) placed on deck face. Fill the void with water (food colour helps visibility) from a burette or syringe, carefully measuring as you go. Its easier on a stand to rotate or rock the block to eliminate bubbles. Fill to lower level of hole. Note this measurement. (a)
Do the same to the head only install plug. If you need to seal the valves, have them ground/lapped. Note measurement (b)
Measure compressed head gasket and calculate volume. (c) Eg. 1.6mm = 9.86cc.
Calculating your swept volume is simple using the actual bore size and stroke. Call this (d)
CR= a+b+c+d / a+b+c
However since your engine is assembled the logical option, IMO. is to do a dry and wet cranking compression test. Approximate CR can be indicated and compared to specs as well as the ring and valve sealing.
Hopefully this aspect will be fine and you can then continue looking for a simpler problem.
Cheers, Roger |
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brit2514
Joined: 21 Feb 2007
Posts: 18
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| Posted: Wed May 16, 2007 7:28 am Post subject: |
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i am sure every thing is timed correct and the compression is ok
i am now having a problem with the throttle response
the car seem to lack power till about 3000-4000rpm then it goes
i have played with the dizzy timing but can't get it any better, any ideas? |
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RC
Joined: 25 Mar 2007
Posts: 2637
Location: Australia
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| Posted: Wed May 16, 2007 12:43 pm Post subject: |
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These symptoms are indicative of retarded cam timimg which will occur as a result of milling your head.
0.075" was it?, will retard your cam timing about 3 deg with a new belt. The teeth on the cam gear are spaced about 8 deg, so to experiment try advancing the cam 1 tooth and see if your powerband moves in the opposite direction- more down low and less up top.
The correct timing will lie somewhere in between these two settings and rectification will involve a variable cam gear.
Dont forget to reset yout ignition timing after altering cam timing.
Roger |
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