Previous Thread
Next Thread
Print Thread
Page 1 of 2 1 2
110 vs 93 octane #2736281
01/24/20 07:15 PM
01/24/20 07:15 PM
Joined: Mar 2011
Posts: 1,321
Michigan
T
Transman Online content OP
pro stock
Transman  Online Content OP
pro stock
T

Joined: Mar 2011
Posts: 1,321
Michigan
Has anyone done any testing, on track or dyno comparing power made using 93 versus 110.

Baseline motor is a hemi, aluminum head, 11.5-1 ratio, cranking compression 180, 2 x 4 inline manifold.

So to be clear, if this engine made x power would you expect it to make more or less on 93 versus the 110 used on the dyno.

BSFC numbers climbed as the engine speed increased, EGT was less than 1100 at 6500.

It didn’t like more than 32 degrees either.

Not sure if the fuel is part of the problem, or maybe just the high speed bleeds, jetting or combination of all.
Jetting was lower than what was called for and while it helped by leaning it out it seemed way too fat for what it was running.



Last edited by Transman; 01/24/20 07:16 PM.
Re: 110 vs 93 octane [Re: Transman] #2736312
01/24/20 08:55 PM
01/24/20 08:55 PM
Joined: May 2019
Posts: 46
Lake Villa Il
INTMD8 Offline
member
INTMD8  Offline
member

Joined: May 2019
Posts: 46
Lake Villa Il
Most of my experience is with calibrating efi cars rather than gen2 Hemi's specifically. That being said I'll throw in my .02.

On naturally aspirated combinations I start with a relatively conservative timing curve and first dial in target wot air fuel ratio.

Once that is done I'll put a few more degrees in and see if power increases (along with watching knock sensor output on the stuff I'm working with).

As long as it isn't getting knock I'll continue to add a degree at a time as long as power is increasing, noting if this is making the same result throughout the rpm range or varying at different rpm ranges.

I've at times been surprised by how much timing something wants to make max power and also, how little an engine required to make max power.

As far as octane playing into this is concerned, I've only seen higher octane add power if as I was increasing timing and seeing power gains I ran into excessive knock/knock sensor output before I reached a -peak- as far as total timing and horsepower is concerned.

I feel many say "race fuel has a slower burn rate". Truth is many factors influence burn rate but most gasolines burn rate is very similar. If anything, some race fuel is tailored to a faster burn rate as there simply isn't enough time for complete combustion at 9000+++ rpm as there is at 5000 rpm.

So, moving on, look at the energy value of the fuel, or BTU's per lb. Regular pump fuel is slightly higher BTU/lb than most race fuel so if the added octane isn't needed for your combination you will generally get slightly less output from using it.

Exception is E85 which has a much lower energy value but also a much lower stoich value which more than compensates for it. (as in you are burning much more of it)


Your engine at 11.5-1, hemi, aluminum head. I would be surprised if you were leaving much on the table with pump 93. I wouldn't expect it to like more than 32-33deg no matter what fuel.

That being said, only way to know is to test it. Run it back to back at the track or dyno. I would probably try something like 260 GT, 100 octane oxygenated if you are willing to spend the money on race fuel, rather than 110, IMO.

Last edited by INTMD8; 01/24/20 08:56 PM.
Re: 110 vs 93 octane [Re: Transman] #2736578
01/25/20 04:22 PM
01/25/20 04:22 PM
Joined: Apr 2005
Posts: 168
Torrance, Ca
F
Fig Offline
member
Fig  Offline
member
F

Joined: Apr 2005
Posts: 168
Torrance, Ca
Dvorak wrote this awhile ago, I thought it’s a good read. http://www.dvorakmachine.com/tech_WhatAboutFuel.shtml


1937 Plymouth R/S Coupe 440/727
Re: 110 vs 93 octane [Re: Fig] #2736623
01/25/20 07:06 PM
01/25/20 07:06 PM
Joined: May 2019
Posts: 46
Lake Villa Il
INTMD8 Offline
member
INTMD8  Offline
member

Joined: May 2019
Posts: 46
Lake Villa Il
Have to disagree a bit. Octane is resistance to pre/ignition or auto detonation before spark due to heat, not burn speed once ignited.

Or/also ability to achieve smooth controlled combustion after spark event.

If you’re on the edge you can see this on a dyno with a stick car as it goes from a bit of a jagged curve to much smoother after introducing higher octane fuel.

Always open to other ideas so if someone can provide any links to info supporting octane vs burn rate I would like to read it smile

Re: 110 vs 93 octane [Re: INTMD8] #2736638
01/25/20 07:50 PM
01/25/20 07:50 PM
Joined: Feb 2017
Posts: 473
Texas
R
RustyM Offline
mopar
RustyM  Offline
mopar
R

Joined: Feb 2017
Posts: 473
Texas
MD8: I think you will find this article both interesting and helpful.
I actually called Vp to talk about it and, can say i "think" i understand better than i did.
Yes, burn rates and vaporization matter and often the ingredients used to raise octane also reduce burn rates /hurt vaporization and thus, cures knocking etc but also makes less power in some applications.
By the same token, they can blend fuels to take high compressions but burn very fast for engines with really high rpm , which is needed because there is so little time at 10k (and up) to burn fuel.

Vp amazed me in explaining what all they can do with fuel blending.
Part of the article your likely most interested in is a few paragraphs down.

Hope this helps a little .
Tuning is a blast!

Rusty

https://dsportmag.com/the-tech/fuel-101-race-gas-octane-and-alternative-fuels-explained/

Re: 110 vs 93 octane [Re: RustyM] #2736721
01/26/20 09:10 AM
01/26/20 09:10 AM
Joined: Jan 2004
Posts: 4,674
fredericksburg,va
C
cudaman1969 Offline
master
cudaman1969  Offline
master
C

Joined: Jan 2004
Posts: 4,674
fredericksburg,va
Got me thinking as to why our Hemi ran better at 37 degrees, maybe the old Sonoco 260 and first out racing gas was a slow burning fuel. RPM=slow burn=more timing. I remember after using Cam II purple it would evaporate out of the cell one week to the next, switched to blue and it never evaporated. As to the OP, I can't see using 93 and not pinging with a true 11.5 unless very little max timing, I'll find out soon since I'm putting together a iron head Hemi 485 cube with 12.5 (down .055" shorter deck height piston, long story) so I'm all ears guys.

Re: 110 vs 93 octane [Re: cudaman1969] #2736750
01/26/20 11:21 AM
01/26/20 11:21 AM
Joined: Feb 2014
Posts: 896
central il.
S
second 70 Offline
super stock
second 70  Offline
super stock
S

Joined: Feb 2014
Posts: 896
central il.
93 @ 11.5 to1 is no problem on an aluminum headed hemi @ 34 advance. Mine is even fine on 91 non ethanol.

Re: 110 vs 93 octane [Re: second 70] #2736755
01/26/20 11:32 AM
01/26/20 11:32 AM
Joined: Jun 2016
Posts: 218
Washington
H
hemienvy Online content
enthusiast
hemienvy  Online Content
enthusiast
H

Joined: Jun 2016
Posts: 218
Washington
Second 70,
What are your cam specs?

Re: 110 vs 93 octane [Re: hemienvy] #2736758
01/26/20 11:42 AM
01/26/20 11:42 AM
Joined: Feb 2014
Posts: 896
central il.
S
second 70 Offline
super stock
second 70  Offline
super stock
S

Joined: Feb 2014
Posts: 896
central il.
Originally Posted by hemienvy
Second 70,
What are your cam specs?


Crane solid roller 112 lobe separation 14 vacuum @ 1100 idle Low rpm motor Lol!

Mike

IMG_2122-1.jpg
Re: 110 vs 93 octane [Re: second 70] #2736772
01/26/20 12:41 PM
01/26/20 12:41 PM
Joined: Jan 2004
Posts: 4,674
fredericksburg,va
C
cudaman1969 Offline
master
cudaman1969  Offline
master
C

Joined: Jan 2004
Posts: 4,674
fredericksburg,va
I see the spring spec but not duel or triple? Mine is set up for a big roller but I’m using a cam similar to yours so I’m thinking something lighter

Re: 110 vs 93 octane [Re: cudaman1969] #2736823
01/26/20 03:08 PM
01/26/20 03:08 PM
Joined: Feb 2014
Posts: 896
central il.
S
second 70 Offline
super stock
second 70  Offline
super stock
S

Joined: Feb 2014
Posts: 896
central il.
Originally Posted by cudaman1969
I see the spring spec but not duel or triple? Mine is set up for a big roller but I’m using a cam similar to yours so I’m thinking something lighter


Dual https://www.summitracing.com/parts/crn-96878-16/

Re: 110 vs 93 octane [Re: cudaman1969] #2736855
01/26/20 05:14 PM
01/26/20 05:14 PM
Joined: Aug 2003
Posts: 34,258
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
I Win
C

Joined: Aug 2003
Posts: 34,258
Bend,OR USA
I've heard the old adage, racers theory, that aluminum heads suck enough heat out of the combustion chambers to equal one full point of compression ratio lower work
My last pump gas motor that made decent power had a true 10.78 to 1 compression ratio in it, it ran real good on straight 92 octane Oregon pump swill with no ethanol alcohol in it with Indy SR heads up


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 110 vs 93 octane [Re: Cab_Burge] #2736876
01/26/20 06:39 PM
01/26/20 06:39 PM
Joined: Oct 2003
Posts: 10,221
W. Kentucky
justinp61 Offline
I Live Here
justinp61  Offline
I Live Here

Joined: Oct 2003
Posts: 10,221
W. Kentucky
My 434" small block made 30 more hp on pump 93 than on Crate 98 race gas. All the tuning on the dyno was done with the 98. We pumped out the fuel cell and drained the carb then put in the 93, started it and allowed it to warm up, then made the pulls on 93. I've ran it on 110 unleaded gas too, the afr's were good but it didn't run the numbers that 93 does.

It's 11.2-1 with a 263/271° @ .050", .711/.719" solid roller.

Re: 110 vs 93 octane [Re: second 70] #2736943
01/26/20 10:55 PM
01/26/20 10:55 PM
Joined: Jan 2004
Posts: 4,674
fredericksburg,va
C
cudaman1969 Offline
master
cudaman1969  Offline
master
C

Joined: Jan 2004
Posts: 4,674
fredericksburg,va
Originally Posted by second 70
Originally Posted by cudaman1969
I see the spring spec but not duel or triple? Mine is set up for a big roller but I’m using a cam similar to yours so I’m thinking something lighter


Dual https://www.summitracing.com/parts/crn-96878-16/

Thanks

Re: 110 vs 93 octane [Re: Cab_Burge] #2736972
01/27/20 04:48 AM
01/27/20 04:48 AM
Joined: Mar 2007
Posts: 2,926
West Coast, USA
jbc426 Offline
master
jbc426  Offline
master

Joined: Mar 2007
Posts: 2,926
West Coast, USA
I'm running 10.2 to 1 that cranks 200 psi on both my Magnum and stroked 493" RB motors. I'm able to run full advance on both motors burning the 91 octane ethanol additive fuel we get he in California with zero detonation. My RB is actually locked out at 35*, and it never even kicks back on start-up.

While the 101 octane street legal race gas that's available at the pump nearby smells way better when burned, it's supposed to make less power than the 91 octane pump gas. The difference is so subtle that I can't feel it in either car.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 3.91's (closest thing to an automatic 5 speed going)
Re: 110 vs 93 octane [Re: jbc426] #2737011
01/27/20 09:52 AM
01/27/20 09:52 AM
Joined: Dec 2004
Posts: 120
Albert Lea, MN
G
GTX5877 Offline
member
GTX5877  Offline
member
G

Joined: Dec 2004
Posts: 120
Albert Lea, MN
As reputed engine builder and tuner, John Lingenfelter, once said

Running an engine on the edge of detonation, will always make more power!

Re: 110 vs 93 octane [Re: GTX5877] #2737259
01/27/20 08:34 PM
01/27/20 08:34 PM
Joined: Aug 2003
Posts: 34,258
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
I Win
C

Joined: Aug 2003
Posts: 34,258
Bend,OR USA
Originally Posted by GTX5877
As reputed engine builder and tuner, John Lingenfelter, once said

Running an engine on the edge of detonation, will always make more power!

How many real car people, not real hard core racers, can tell the difference between the edge of and in detonation ?
A hot humid day can take a N/A carbureted motor on the edge of detonation deep enough into detonation so bad that you can hear it pinging shock
Way better to be on the safe side on the street, IMO up

Last edited by Cab_Burge; 01/27/20 08:35 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 110 vs 93 octane [Re: Cab_Burge] #2737354
01/28/20 08:31 AM
01/28/20 08:31 AM
Joined: Jan 2003
Posts: 11,690
Marion, South Carolina [><]
an8sec70cuda Online content
I Live Here
an8sec70cuda  Online Content
I Live Here

Joined: Jan 2003
Posts: 11,690
Marion, South Carolina [><]
Not scientific at all, but mine slowed down almost a tenth and 1 mph when I put some 110 in the tank after running low on pump 93.
11:1 572" hemi at 34° running mid 9s at 140 mph. I didn't adjust anything for the fuel change b/c it's a dedicated pump gas motor.


CHIP
'70 hemicuda street car...8.91 at 150.5 mph w/ 4.10s, 8.97 at 152.5 mph w/ 3.54s so far
'69 road runner 440 w/ Indy SRs
'69 road runner 440-6, 4 speed...Dad's ride
'71 Demon 340 resto project
'06 GMC 2500HD LBZ Duramax...toy hauler
'16 Grand Caravan SXT...baby hauler
Re: 110 vs 93 octane [Re: an8sec70cuda] #2737401
01/28/20 11:09 AM
01/28/20 11:09 AM
Joined: Feb 2010
Posts: 1,540
Phila. Pa.
Mattax Offline
pro stock
Mattax  Offline
pro stock

Joined: Feb 2010
Posts: 1,540
Phila. Pa.
.Choosing the correct gasoline, Motorsports Village archive

I made a graphic of some pump fuels and race fuel distillation curves.
That helped me understand the references to the heavy end characteristics discussed in that thread.

Fuel-distillation-Race-AV-2007.png
Re: 110 vs 93 octane [Re: an8sec70cuda] #2737416
01/28/20 12:04 PM
01/28/20 12:04 PM
Joined: Jan 2004
Posts: 4,674
fredericksburg,va
C
cudaman1969 Offline
master
cudaman1969  Offline
master
C

Joined: Jan 2004
Posts: 4,674
fredericksburg,va
Originally Posted by an8sec70cuda
Not scientific at all, but mine slowed down almost a tenth and 1 mph when I put some 110 in the tank after running low on pump 93.
11:1 572" hemi at 34° running mid 9s at 140 mph. I didn't adjust anything for the fuel change b/c it's a dedicated pump gas motor.

Good to know, I’ll be close to that

Page 1 of 2 1 2

Advertisement
Sponsored Link
Moparts Newest Topics
Cuda 340 shaker feet brackets
by AARCONV. 02/27/20 08:06 AM
1964 Polara Convertible with Max Wedge
by 65pacecar. 02/27/20 07:26 AM
66 Valiant - $700
by not_a_charger. 02/27/20 07:04 AM
1970 Dodge Coronet Superbee Engine 440
by tomsjack. 02/27/20 03:32 AM
Moparts Recent Posts
'73 Duster 340 actually IS a survivor
by mopars4ever. 02/27/20 08:28 AM
New Passon Performance 5 Speed update
by OhioMopar. 02/27/20 08:25 AM
long rod 400, 915 heads
by hemienvy. 02/27/20 08:21 AM
CARB SOAK
by ChrgrCuda. 02/27/20 08:20 AM




Powered by UBB.threads™ PHP Forum Software 7.7.1