Lars...Will this really increase mpg
Instructor
Joined: Jul 2005
Posts: 124
Likes: 0
What about spacers like this one, where it has 4 holes, but the holes are not straight, but angled instead.
http://cgi.ebay.com/ebaymotors/Carbu...spagenameZWDVW
Would that angle be good?
http://cgi.ebay.com/ebaymotors/Carbu...spagenameZWDVW
Would that angle be good?
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
report updated again
http://community.webtv.net/MATTGRU/carb
I added a wood 0.2" 4 hole to my 72 today.
While i was at it i put in .002" smaller very lean .054" primary jets
same as my 61.
When cold, as i don't have a choke, this causes a slight tip in ~1/8" of the pedal to up cruise speed(PV opens at 13"). Cruise is steady, no surge or miss. So i'll do a mpg test soon, but it got 14.2 before. Even if mpg doesn't go up, it now has an insulator and bowl heat shield
and with only a 0.17" rise, the hood still closes 
http://community.webtv.net/MATTGRU/carb
I added a wood 0.2" 4 hole to my 72 today.
While i was at it i put in .002" smaller very lean .054" primary jets
same as my 61.When cold, as i don't have a choke, this causes a slight tip in ~1/8" of the pedal to up cruise speed(PV opens at 13"). Cruise is steady, no surge or miss. So i'll do a mpg test soon, but it got 14.2 before. Even if mpg doesn't go up, it now has an insulator and bowl heat shield
and with only a 0.17" rise, the hood still closes
Last edited by Matt Gruber; Nov 26, 2007 at 10:16 AM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Pro
Joined: Oct 2007
Posts: 587
Likes: 0
From: Overland Park Kansas
Right now, somewhere between 8-10mpg with mixed city and highway.
I just installed the spacer, and took off the aluminum one that was on there. Apparently I was wrong, this is what I pulled off the car:
I thought it was a 2 hole, but it's just completely open. The middle divider on my performer intake wasn't doing anything because there was no seal at all.
Also, I know you guys are going to think I'm psycho, but my brakes are working better when I took it out for a test drive. Am I just crazy or could this possibly affect the braking system?
I just installed the spacer, and took off the aluminum one that was on there. Apparently I was wrong, this is what I pulled off the car:
I thought it was a 2 hole, but it's just completely open. The middle divider on my performer intake wasn't doing anything because there was no seal at all.
Also, I know you guys are going to think I'm psycho, but my brakes are working better when I took it out for a test drive. Am I just crazy or could this possibly affect the braking system?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Did you happened to check your manifold vacuum before and after the change?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Pro
Joined: Oct 2007
Posts: 587
Likes: 0
From: Overland Park Kansas
No, I really wish I would have but I forgot. It takes like 10m to swap though, so maybe I will later.
Just realized now though that the engine is pinging on acceleration. It wasn't doing that with the old carb spacer. I guess I'll have to retard the timing a little. Should the carb spacer affect that?
Just realized now though that the engine is pinging on acceleration. It wasn't doing that with the old carb spacer. I guess I'll have to retard the timing a little. Should the carb spacer affect that?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
No, I really wish I would have but I forgot. It takes like 10m to swap though, so maybe I will later.
Just realized now though that the engine is pinging on acceleration. It wasn't doing that with the old carb spacer. I guess I'll have to retard the timing a little. Should the carb spacer affect that?
Just realized now though that the engine is pinging on acceleration. It wasn't doing that with the old carb spacer. I guess I'll have to retard the timing a little. Should the carb spacer affect that?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Just keep backing up the timing until it stops pinging-then check your total timing with vacuum hooked up.If your not close to Lars number of 52 then you will probably have to make some changes.When you got it set up did you change the vac. can or are you using the original?
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
very good news! i couldn't ask for a better candidate for mpg gains. look for mpg in the teens.
with 11:1 timing must be set right.
with less reversion, the A/F has leaned out lots! Good! A too rich mixture stops pinging, but, it is an expensive way to do it.
Might not have to rework carb. Don't insist on lars' timing #'s. He does HP tunes, not mpg tunes. U can have BOTH high HP and good mpg, but nobody demands BOTH so they don't get both. I run as low as 31 degrees(vs. 36), so don't be afraid to back it off. Even the high 20's could get it into the teens mpg.
Does this mean everyone should run less timing to get more mpg? (homer simpson asks)
No. To get good mpg it has to run lean at cruise. Then it will ping easier on modest acceleration(not enough throttle for power enrichment). So timing must be set as per that particular combo, not generic #'s.
with 11:1 timing must be set right.
with less reversion, the A/F has leaned out lots! Good! A too rich mixture stops pinging, but, it is an expensive way to do it.
Might not have to rework carb. Don't insist on lars' timing #'s. He does HP tunes, not mpg tunes. U can have BOTH high HP and good mpg, but nobody demands BOTH so they don't get both. I run as low as 31 degrees(vs. 36), so don't be afraid to back it off. Even the high 20's could get it into the teens mpg.
Does this mean everyone should run less timing to get more mpg?
(homer simpson asks)No. To get good mpg it has to run lean at cruise. Then it will ping easier on modest acceleration(not enough throttle for power enrichment). So timing must be set as per that particular combo, not generic #'s.
Last edited by Matt Gruber; Nov 28, 2007 at 08:52 AM.
Pro
Joined: Oct 2007
Posts: 587
Likes: 0
From: Overland Park Kansas
Yeah I was curious about that actually. I don't really know what timing I should shoot for with my 383. With my high compression, should I try to get 36 total timing w/o vacuum, and 52 total timing w/vacuum?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
This will be a fun one to follow and some great stuff for Matts website.
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
U guys don't get it. U can't get help from someone that doesn't have any interest in, or knowledge of, this topic.
He has a lot of catching up to do to make a helpful response; and he isn't interested in mpg. Got it?
He has a lot of catching up to do to make a helpful response; and he isn't interested in mpg. Got it?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Lars and MPG
Imagine if he focused on getting better gas milage-The fuel companys would HAVE to put out a HIT on him.
Pro
Joined: Oct 2007
Posts: 587
Likes: 0
From: Overland Park Kansas
Well to be honest I'm not here to bash anyone. I'm trying Matts idea so that shows I am willing to try, but I also need timing help and I know Lars is apprently the go-to guy for timing.
I really don't care who makes the suggestion on what I should run, I just want the suggestion
I really don't care who makes the suggestion on what I should run, I just want the suggestion
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
1st
I'm not bashing lars; he is a great guy! But, if lars wanted to, he would have tried the 4 holer weeks ago(maybe years ago, or decades ago). HE IS NOT INTERESTED! GOT IT? His tuning is VERY successful as long as u don't demand top mpg.
.
First map out the pinging.
What rpm? WOT?
accel from cruise? all rpm's or just some.
Then plot the advance curve w/timing light, no vac advance.
i'll take a guess at 17 base 32 total.
i'd set the base at 20, and set the weights for another 15, that's 35, and i figure it will ping, but u won't know until u try. turn the dis CW-clockwise, until it stops pinging, or rarely pings slighty.
DISCONNECT the vac advance for ping testing.
CLUE: sometimes it is causing the ping and the can has to be changed.
Myself, I'd want to do a quick mpg check, so i'd just turn the dist CW and see if it stops pinging and runs fair enough for a mpg test. Precise tuning may add ~1-2 mpg, and better drivability, but why bother today, when all the fun is the mpg?
I'm not bashing lars; he is a great guy! But, if lars wanted to, he would have tried the 4 holer weeks ago(maybe years ago, or decades ago). HE IS NOT INTERESTED! GOT IT? His tuning is VERY successful as long as u don't demand top mpg.
.
First map out the pinging.
What rpm? WOT?
accel from cruise? all rpm's or just some.
Then plot the advance curve w/timing light, no vac advance.
i'll take a guess at 17 base 32 total.
i'd set the base at 20, and set the weights for another 15, that's 35, and i figure it will ping, but u won't know until u try. turn the dis CW-clockwise, until it stops pinging, or rarely pings slighty.
DISCONNECT the vac advance for ping testing.
CLUE: sometimes it is causing the ping and the can has to be changed.
Myself, I'd want to do a quick mpg check, so i'd just turn the dist CW and see if it stops pinging and runs fair enough for a mpg test. Precise tuning may add ~1-2 mpg, and better drivability, but why bother today, when all the fun is the mpg?
Last edited by Matt Gruber; Nov 28, 2007 at 12:57 PM.