Author |
Message |
TomjS Samba Member
Joined: December 20, 2023 Posts: 3 Location: Guildford, UK
|
Posted: Fri Dec 22, 2023 10:00 am Post subject: Is rolling road carb tuning worth it? |
|
|
Hi everyone,
Looking into servicing the engine in a 77 Bay with a 2 litre dual carbs for the first time and I have seen carb tuning mentioned a couple times. What are your thoughts on getting the carbs tuned professionally on a rolling road? Is it worth the high costs (~£350 for www.aireytuning.com !!) in the long run, or will DIY do it well enough?
Many thanks in advance,
Tom |
|
Back to top |
|
|
busman78 Samba Member
Joined: August 17, 2004 Posts: 4524 Location: Oklahoma City, OK
|
Posted: Fri Dec 22, 2023 10:23 am Post subject: Re: Is rolling road carb tuning worth it? |
|
|
Do it yourself and learn, save the dollars. |
|
Back to top |
|
|
busdaddy Samba Member
Joined: February 12, 2004 Posts: 51153 Location: Surrey B.C. Canada, but thinking of Ukraine
|
Posted: Fri Dec 22, 2023 10:46 am Post subject: Re: Is rolling road carb tuning worth it? |
|
|
What kind of carbs (stock, afrtermarket)?, who's been working on it in the past? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
|
Back to top |
|
|
KTPhil Samba Member
Joined: April 06, 2006 Posts: 34021 Location: Conejo Valley, CA
|
Posted: Fri Dec 22, 2023 1:10 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
busman78 wrote: |
Do it yourself and learn, save the dollars. |
Yes, these need periodic adjustments, so it will need re-tuning anyway. Proper jetting, balancing, adjusting idle mixture and speed are all do-able at home.
Learning how to take it from start to finish yourself will be valuable down the road, either to tune it again later, or save it on the side of the road. |
|
Back to top |
|
|
mikedjames Samba Member
Joined: July 02, 2012 Posts: 2745 Location: Hamble, Hampshire, UK
|
Posted: Fri Dec 22, 2023 2:08 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
Buy and fit an Air Fuel Ratio meter, and get a carburettor synchroniser tool.
Cheaper and any day can be a tuning day if you wish. _________________ Ancient vehicles and vessels
1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.
1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy |
|
Back to top |
|
|
SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
|
Posted: Fri Dec 22, 2023 5:07 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
do you know how to tune and sync the two carbs other than main jets? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
Back to top |
|
|
metahacker Samba Member
Joined: May 26, 2010 Posts: 692 Location: san.diego
|
Posted: Fri Dec 22, 2023 9:54 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
Having your vehicle tuned for the proper air-fuel ratios and ignition timing (using a wideband and a dyno) is the best thing you can do to a running engine keeping it "as-is"
most particularly, an air-cooled one
water cooled engines have extra capacity for cooling with large radiators and lots of coolants buffering temperatures, and a thermostat always working to apply the cooling system only as much as needed .. the state of tune on these engiens can change quite a bit without really having a dramatic impact on cylinder head temperatures in normal operating conditions
An air-cooled Bus engine cruising the highway, however, is just blowing a fixed amount of air onto itself from the engine fan based on RPM, and the cylinder head temperature is basically whatever you get based on how hot its running vs what RPM the fan is at.. the thermostat is is not in play under those conditions....
small tuning changes can have pretty dramatic impacts on engine temperatures with a Bus, as tuning is the part of the formula for real life cylinder head temperatures that you can actually have the most control over
the difference in drivability and efficiency can be pretty dramatic, too
don't listen to people say that you tune it by ear, DIY, at home driving around the block and reading spark plugs
that isn't the same thing at all
no substitute for...
ROLLING ROAD
WIDEBAND
DATA LOGGING,
tuning BY the NUMBERS. as inrejetting..not just setting idle/mixture screws and acting like that's what "tuning" a carb means.
that will definitely produce results !!!
As a general rule, target 0.80 - 0.89 Lambda values for fuel and you will be solid
Once your carb is feeding the correct fuel ratios across all loads
then you can do your ignition, using "MBT" (look it up)
if you have a 123 distributor then you can do a totally custom map to follow MBT exactly
if you have an OEM distributor you can just spin it and advance until you find the absolute minimum amount of static advance where you have basically the max torque value
you can futz with weights and springs to really customize the map, but at that point the 123 is a much better choice
the ignition timing isn't usually that serious, though .. it's the carb tuning that can vary greatly. a stock distributor at stock specs is always fine but get those air-fuel ratios PERFECT...and it will be great.
if someone else it doing it all, and knows your carbs, then great
in the UK, this seems to be a a much more common practice, and there seem to be a lot of people doing that sort of work.. |
|
Back to top |
|
|
TomjS Samba Member
Joined: December 20, 2023 Posts: 3 Location: Guildford, UK
|
Posted: Sun Dec 24, 2023 11:34 am Post subject: Re: Is rolling road carb tuning worth it? |
|
|
Thanks for the responses everyone. I have twin Dellorto DRLA 40s and we recently bought the bus so this is the first time I am doing this. My current plan is to install a wideband sensor and log the readings whilst driving a set bit of road. Do you think this will suffice or is a rolling road much better?
Thanks again and have a good Christmas!
Tom |
|
Back to top |
|
|
orwell84 Samba Member
Joined: May 14, 2007 Posts: 2539 Location: Plattsburgh, New York
|
Posted: Sun Dec 24, 2023 1:00 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
I agree with going with an AFR gauge and maybe dyno tuning…at a certain point.
Lots of bus engines don’t run as well as they could because of tuneup and maintenance 101 kinds of issues; timing, vacuum leaks, missing tin, improperly adjusted valves. You would want to make sure all of these are put right as well as having healthy compression on all 4 cylinders.
I would want to have all these things sorted out with the bus running the best I could get it before spending the money on a dyno tune. Since your bus is new to you, you are likely to have some of the issues mentioned above. At the very least, these skills are a requirement if you want to drive your bus any distance. |
|
Back to top |
|
|
airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12728 Location: on a bike ride somewhere
|
Posted: Sun Dec 24, 2023 3:46 pm Post subject: Re: Is rolling road carb tuning worth it? |
|
|
Depends on where your wideband bung is. Tailpipe clamps get less accurate the faster you go, but an O2 sensor at a header collector or pre-cat/muffler would be great.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
Back to top |
|
|
|