 |
924Board.org
Discussion Forum of 924.org
|
| View previous topic :: View next topic |
| Author |
Message |
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
|
| Back to top |
|
 |
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
 Posted: Sat Mar 04, 2006 7:58 pm Post subject: |
 |
|
Yeah ,
His work is good , applied knowledge bad ! The cis is direct port carburation
making your fuel curve uneven at different rpm's, fuel is applied in the quantity dictated by the flap regardless of engine requirement vs load. too much here , too little there etc. I would not give shelf space to a cis system !
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Sun Mar 05, 2006 8:58 am Post subject: |
|
|
The shape of the slits on the cylinder wall can be changed at different levels to the fuel ratio at different levels. The 928 (and Mercedes?) distributor have narrow rectangular metering slits. If these were machined to a bowling pin shape the air fuel mixture would be increased at a higher midrange rpm. Also a trapazoid shaped slit would cause a steady A/F ratio increase as the rpms rise. Any changes like this would require recalibration of the orifice at the valves and possible adjustment of the valve spring rate. But yes, the CIS can be machined to provide more fuel on turbo charged engines.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
| Posted: Sun Mar 05, 2006 9:28 am Post subject: |
|
|
| dpw928 wrote: | The shape of the slits on the cylinder wall can be changed at different levels to the fuel ratio at different levels. The 928 (and Mercedes?) distributor have narrow rectangular metering slits. If these were machined to a bowling pin shape the air fuel mixture would be increased at a higher midrange rpm. Also a trapazoid shaped slit would cause a steady A/F ratio increase as the rpms rise. Any changes like this would require recalibration of the orifice at the valves and possible adjustment of the valve spring rate. But yes, the CIS can be machined to provide more fuel on turbo charged engines.
Dennis |
Ohh yeah , i would like to see that , as any turbo will pull that flap wide open at peak boost in the mids where it i will be too rich causing excessive lag,
The flap does not open due to rpm but by load causing too much , here not enough there etc. but mostly the high fuel pressure needed to run a cis system limits flow so big HP numbers are out the window.
unless you are happy with 450 to 500 out of a v8 engine, just don't leave the house or venture any where near So. FLA you will not be happy.
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Sun Mar 05, 2006 9:54 am Post subject: |
|
|
The flap opens due to air movement, not boost pressure. My concern was the delivery of extra fuel due to the pressure on the distributor piston, but this proved not to be true on the converted engines.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
| Posted: Sun Mar 05, 2006 1:28 pm Post subject: |
|
|
| dpw928 wrote: | The flap opens due to air movement, not boost pressure. My concern was the delivery of extra fuel due to the pressure on the distributor piston, but this proved not to be true on the converted engines.
Dennis |
Dennis not trying to be rude here , but where is the little itty bitty turbo sucking air from to make boost pressure ! ohh yes that 's right from the air flow meter and what causes the air flow meter to go WO , that's right the load!
Ok , so now we have WOT , full load , air flap wide open injectors spraying for all it's worth and the engine is at 3000 rpm , guess what , turbo lag due to being overly rich and boom now full boost 7000 rpm now what happens lean mixture , now engine goes boom for the last time.
because if you set the system to produce a rich mixture at 7000 it will be too rich at 3000 rpm, et al.
My point the CIS cannot fuel any engine correctly based on load vs rpm and mostly it is for low power application at best.
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Sun Mar 05, 2006 5:58 pm Post subject: |
|
|
You are confusing pressure (boost) with velocity (air movement). The sensor plate is only opening dependant upon how much air actually enters the cylinders regardless of boost/pressure in the intake. I was suspicious also, but there are supercharger boosted 928's running with this configuration. Check the archives on the Rennlist 928 forum.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
| Posted: Mon Mar 06, 2006 1:14 am Post subject: |
|
|
| dpw928 wrote: | You are confusing pressure (boost) with velocity (air movement). The sensor plate is only opening dependant upon how much air actually enters the cylinders regardless of boost/pressure in the intake. I was suspicious also, but there are supercharger boosted 928's running with this configuration. Check the archives on the Rennlist 928 forum.
Dennis |
I'm not confusing anything dennis and you are getting into semantics , the more boost the more air the more the sensor plate moves , you have not done one of these on a dyno pull to see the plate movement , the sensor plate is load dependant and the plate movement is very much dependant on boost pressure or how much thereof, anyway anyone running a cis system for a turbo application is behind the plate , so to speak pun intended.
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Mon Mar 06, 2006 1:33 am Post subject: |
|
|
No semantics here, just physics. Additionally, the air sensor plate has counter (control) pressure of 3 to 3.5 bar pushing it closed unless there is air movement. BTW I posted the link for the guys inquiring about the 928 fuel distributors on the 931 GT's. If you don't think boosting a CIS will work, tell it to the guys on Rennlist that are already supercharging them.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
| Posted: Mon Mar 06, 2006 2:19 am Post subject: |
|
|
| dpw928 wrote: | No semantics here, just physics. Additionally, the air sensor plate has counter (control) pressure of 3 to 3.5 bar pushing it closed unless there is air movement. BTW I posted the link for the guys inquiring about the 928 fuel distributors on the 931 GT's. If you don't think boosting a CIS will work, tell it to the guys on Rennlist that are already supercharging them.
Dennis |
Dennis if you are trying to argue the merits of CIS ok
Merits : blah .......
ok now the demerits of CIS
___blah , blah , blah ,blah, to infinity
1978 - Turbo Charged my FIrst VW Scirroco CIS System ( 14.7 et's )
1979 - Started to mod said CIS system via control pressure mods.
1980-82 - CIS mods with larger injectors along with euro boost reference control pressure regulator.13.2 et's starting doing callaway systems on BMW's along with VW's
1982- Had enough CIS know how on anything that had one,spent many nites wide eyed , knowing there had to be a better way, Did the Bosch school deal , had the books made the jobs work but aaaaggghhh.
84-86 931 turbo time and yes we did the v-8 mod on the 924 twenty years ago ( mercedes fuel head 450 sel ) played played , played .
88- present EFI wow! Programmable EFI systems CIS spat - pooh, pooh
spit, dunk , Germany's way of getting back at the west for WW1 and 2
So please , i do not need to be taught OR LECTURED ON anything REGARDING CIS and i don't care who is using it , in 2006 it does not change the limitations on the system and yes A 928 with cis with turbo 1979 , been there done that ! So now 20 odd years later , someone is turbocharging a cis 928 and i'm to be impressed ! well i like hot rodders and if that is what they are doing then i' m happy for them , but that does not change the demerits of the CIS and i'm not telling them not to turbocharge there 928 with CIS , just stating a fact that in 06 there is mucho EFI systems to choose from at all levels.
And remember the cis is all about system pressure, THIS IS WHY YOUR HP IS LIMITED WITH IT TRYING TO MAINTAIN 5 BAR PLUS FUEL PRESSURE
WHILE REFERENCING BOOST, IS WELL, less move on this is starting to get winded, i'm sure you are happy working with the CIS system Dennis
best of luck and for those wanting to do the v8 mod on a cis system they will have fun, but the money would be better spent going EFI.
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Mon Mar 06, 2006 4:17 am Post subject: |
|
|
| Quote: | | Dennis if you are trying to argue the merits of CIS ok |
Since when is discussing the operation of the CIS system considered to be arguing its merits?
I posted the link for the guys wanting to convert an engine to the GT version. If you have a problem with the guys on the 928 forum boosting a CIS system why aren't you over there telling them it won't work? Before you post there I would recommend you do your homework.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
sequential
Joined: 18 Nov 2005
Posts: 500
Location: BANNED
|
| Posted: Mon Mar 06, 2006 5:27 am Post subject: |
|
|
| dpw928 wrote: | | Quote: | | Dennis if you are trying to argue the merits of CIS ok |
Since when is discussing the operation of the CIS system considered to be arguing its merits?
I posted the link for the guys wanting to convert an engine to the GT version. If you have a problem with the guys on the 928 forum boosting a CIS system why aren't you over there telling them it won't work? Before you post there I would recommend you do your homework.
Dennis |
Dennis
That 's funny , when does stating that a CIS system is a waste of time on a 924 forum , get's me involved with turbo 928's on the rennlist leading to homework. what's next a carburator expert who profile's his jets .Ha. Ha, HA, I mean after suggesting that there are guys on the 928 forum using the CIS system , stupid of me to think it had your approval, as to me having a problem with 928 guys boosting a CIS car never said i did and frankly don't care, I just said it was not worth the time to invest into a cis system because the full benefit's of turbocharging a 928 would not be realised that way. A Turbocharged 928 should /will be a fast car it is a shame to waste time with the CIS on it..
As for my homework Mrs Robinson said it was not due until march 7th
let me know if it is different , don't want to be late.
_________________
928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2
Last edited by sequential on Mon Mar 06, 2006 5:59 am; edited 1 time in total |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Mon Mar 06, 2006 5:57 am Post subject: |
|
|
As my mom once said after she went to mow the new neighbors' small back yard while they were off on an emergency trip, only to have fuel spill out on the grass, killing it while filling because the fuel line on their mower was loose, "Well, no good deed goes unpunished...". 
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
|
| Posted: Mon Mar 06, 2006 7:13 am Post subject: |
|
|
Smoothie,
Amen to that!!!
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
|
| Back to top |
|
|
helowrench
Joined: 25 Nov 2004
Posts: 44
Location: Dallas
|
| Posted: Tue Mar 07, 2006 4:50 am Post subject: |
|
|
sequential,
What they are trying to get across is,
You ahev said your piece, we can tell that you do not like CIS.
okay done.
Leave those of us that DO want to work with it to our discussion.
thanks
Rob |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
