Calling All Dellorto Pros
#26
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
I thought that a struggle that high isnt suprising with out having the header installed. I can try upping the PSI though. Spark plug wires I don't remember off hand. I got them last fall from O'Reilly. BWD brand I think
#27
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,903
Received 2,644 Likes
on
1,873 Posts
try upping the fuel pressure to like 3 and see what happens.
#28
Blood, Sweat and Rotors
iTrader: (1)
Ok here is the updates as of today.
Upgraded the fuel pump, and its regulated to 2.5psi
I jetted the carb main jets to 180 to see what happened, it was noticeably worse. If I pegged it while holding the rpms at 4000, it would kill the engine. However, when I put the 250s in, its not fixed, but it is better. It only kills if i hold it at anything under 3k and peg it. Not much better than 230's
Idle jets are set to 75, and the idle is silky smooth at 1000rpm. Idle screws adjusted as such
.
Upgraded the fuel pump, and its regulated to 2.5psi
I jetted the carb main jets to 180 to see what happened, it was noticeably worse. If I pegged it while holding the rpms at 4000, it would kill the engine. However, when I put the 250s in, its not fixed, but it is better. It only kills if i hold it at anything under 3k and peg it. Not much better than 230's
Idle jets are set to 75, and the idle is silky smooth at 1000rpm. Idle screws adjusted as such
.
\
Also, with that long manifold and 39mm chokes the engine does not like when you stab the gas pedal a low rpms.
#29
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
I dont necessarily have to stab the gas to get the same result I should mention. If I ease into the pedal the same thing will happen. Its like a certain amount of throttle causes the issue. So it must be something mixture related it seems.
What doesnt make sense is if i give it enough gas to kill it, and let off, it will return to idle, but theres no smoke from unburned fuel out of the exhaust. Its almost as though its rich at idle, and then super lean when the progression hits. It seems very odd though. 180 jets made it bog from 4k and less, 250 makes it bog from 3k and less. So I need some massive jets it seems. Just doesnt seem right.
What doesnt make sense is if i give it enough gas to kill it, and let off, it will return to idle, but theres no smoke from unburned fuel out of the exhaust. Its almost as though its rich at idle, and then super lean when the progression hits. It seems very odd though. 180 jets made it bog from 4k and less, 250 makes it bog from 3k and less. So I need some massive jets it seems. Just doesnt seem right.
#30
Blood, Sweat and Rotors
iTrader: (1)
The progression circuit is running lean. Buy Larger idle jets. Try an 80. You tune your main circuit with the main fuel and main air jets, at wide open throttle. TUne the progression circuit with the idle fuel jet and the idle jet holder. The progression circuit controls light throttle steady cruise as well as throtle tip-in.
Your 250 main fuel jet is a band aid.
Your 250 main fuel jet is a band aid.
#31
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,903
Received 2,644 Likes
on
1,873 Posts
the idle circuit works from the POSITION of the throttle plate and intake vacuum. the throttle plate next to the idle/progression hole is what creates the low pressure to pull fuel out. the problem with this is that once the throttle plate moves more open, the there is less vacuum on the hole, so it meters less fuel.
the main circuit basically works off the velocity if the air going thru the carb (its actually the pressure differential between the float bowl and the boosterish), and as such IT DOES NOT WORK when the throttle is closed, as there isn't enough signal.
so what you are experiencing is that the throttle is moving away from the idle/progression holes, so they stop working, AND the main circuit hasn't yet started to meter fuel. which = the car stops running. AND you can be really rich on both sides of the lean spot (you can actually get it to be a rich spot ) and still have it so lean it won't run.
THE FIX?
so what we do with the webers is pull the main jet stack out and go drive it. this disables the main circuit completely. this will show you in like 20 feet exactly what the idle circuit is doing. make notes. once you get out of the idle circuit the car will stop running.
the second test is for the mains, put em back, and bring it up to an RPM a little before where the idle circuit stops, floor it, if the jetting is right it'll just go. if its wrong it'll go for a second and then stop running.
so once you have an idea what the engine wants, then you can approach a fix. a smaller main air corrector will make the mains come on earlier, a bigger idle fuel jet will deliver more fuel on the idle circuit, so it will stay on later.
i suggest you actually try all the jets you have, trying one thing at a time, and as you learn what the engine wants and what each part does it becomes really easy. i kept a little journal with mine.
#32
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
So more than likely I just need smaller main air corrector it seems. Makes sense. I am however going to take this carb back off the car and tear it down completely and have it cleaned. Just one more variable to knock out. I also will have the cash pulled together for a header at the beginning of April hopefully.
#33
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,903
Received 2,644 Likes
on
1,873 Posts
So more than likely I just need smaller main air corrector it seems. Makes sense. I am however going to take this carb back off the car and tear it down completely and have it cleaned. Just one more variable to knock out. I also will have the cash pulled together for a header at the beginning of April hopefully.
in the tuning process for mine, ive rebuilt the carb a few times. be picky, and clean is important, but everything must WORK too.
#37
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,903
Received 2,644 Likes
on
1,873 Posts
#38
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
I wouldnt trust myself that much lol. I also called racingbeat yesterday for kicks and they informed me they haven't done anything with dellortos in 19 years and he couldnt even look up the jetting guide lol.
Oh well, I ordered the rebuild kit yesterday and I'll be having a local VW shop rebuild it for $100 they tell me. Also by the time this is all done, I'll probably have my header as well. Hopefully I won't need to post in this thread anymore but we'll see lol.
Thanks a ton for the help guys.
Oh well, I ordered the rebuild kit yesterday and I'll be having a local VW shop rebuild it for $100 they tell me. Also by the time this is all done, I'll probably have my header as well. Hopefully I won't need to post in this thread anymore but we'll see lol.
Thanks a ton for the help guys.
#40
Jolly Green Giant
iTrader: (1)
Join Date: Feb 2008
Location: San Antonio, TX
Posts: 509
Likes: 0
Received 0 Likes
on
0 Posts
I wouldnt trust myself that much lol. I also called racingbeat yesterday for kicks and they informed me they haven't done anything with dellortos in 19 years and he couldnt even look up the jetting guide lol.
Oh well, I ordered the rebuild kit yesterday and I'll be having a local VW shop rebuild it for $100 they tell me. Also by the time this is all done, I'll probably have my header as well. Hopefully I won't need to post in this thread anymore but we'll see lol.
Thanks a ton for the help guys.
Oh well, I ordered the rebuild kit yesterday and I'll be having a local VW shop rebuild it for $100 they tell me. Also by the time this is all done, I'll probably have my header as well. Hopefully I won't need to post in this thread anymore but we'll see lol.
Thanks a ton for the help guys.
#41
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
I'll get some once I upgrade to an RX3 someday lol
I rebuilt one before, but the shop I took it to I trust with my life. Theyre awsome. I figure they could use the business in this economy and it saves me time. This way I know it'll get good and clean too
I rebuilt one before, but the shop I took it to I trust with my life. Theyre awsome. I figure they could use the business in this economy and it saves me time. This way I know it'll get good and clean too
#43
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
They know my car and rotaries pretty well. The owner of the shop had an rx3 back in the day that he ran aftermarket carbs on. Just so I'm clear, the only thing they need to keep is the needle/seat, e tubes, and remake the extra gasket for the AP correct?
#45
Fighting Global Cooling
Thread Starter
iTrader: (6)
Join Date: Mar 2009
Location: Minneapolis, Minnesota
Posts: 983
Likes: 0
Received 0 Likes
on
0 Posts
I'm sure they won't. Theyre basically just going to give it a very thorough cleaning and put in the new gaskets. I'll just make sure they know about the mods