Spec Miata Community   
search | help | calendar | games | forum home

  next oldest topic   next newest topic
» Hello Spec Miata Community » SpecMiata.com » Spec Miata » Ethanol fuel

 - Email this page to someone! | Subscribe To Topic  
Author Topic: Ethanol fuel
cintibob
Member

Region: cfr
Car #: 13
Year : 1990
Posts: 105
Status: Offline
Icon 1 posted  Profile for cintibob     Edit/Delete Post  Report this post to a Moderator

At the last race at Sebring I needed to buy gas so I went over to the track station and bought 93 octane and noticed it did not contain 10% alcohol. I usually buy 93 octane at home and run 16 degrees timing just because that is the timing the car likes and do not want to buy expensive 100 octane. I have found a place near home that I can purchase gas with no alcohol which got me to thinking has anyone really tested 93 octane (10% ethanol) to 93 or 87 non ethanol in their car on a dyno.I have a 1.6L car and did not notice any difference on track. I charted top speeds at the end of the straights for both types of gas and avg. all the laps with only very minor difference, in the tenths of a MPH. And I only had one lap faster with non ethanol by a second but that session I was close to two cars and drafting could have affected that. Also who runs 87 octane and at what advance in timing. I would think at any timing over stock 87 octane would cause pinging. Also has any one gotten bad gas or gas with water in it from the station? Recently all stations have had to change tanks so I am not sure that there has been enough time for tanks to have enough water in them. I did a search on this subject and it seem to be all over the place so I have tried to keep it to 93 or 87 octane.

Gatoratty Verified Driver Made Donation to Website
Member

Region: Central Florida
Car #: 3
Year : 1992
Posts: 1304
Status: Offline
Icon 1 posted  Profile for Gatoratty     Edit/Delete Post  Report this post to a Moderator

Jamie Tucker told me that he has tested all kinds of gas on the dyno and that 87 octane is best for a 1.6. Not sure about ethanol vs. no ethanol.

--------------------
Paul McLester

oem steve
Member

Region: South East
Car #: #92
Year : 91
Posts: 189
Status: Offline
Icon 1 posted  Profile for oem steve     Edit/Delete Post  Report this post to a Moderator

I run 87 octane in my car, it actually made the most HP with it on the dyno, of course thats not saying much [banghead]

--------------------
email: standrewsexpress@bellsouth.net
visit us at http://www.standrewsexpress.com

Under powered and under driven

cintibob
Member

Region: cfr
Car #: 13
Year : 1990
Posts: 105
Status: Offline
Icon 1 posted  Profile for cintibob     Edit/Delete Post  Report this post to a Moderator

OEM; what timing do you run with 87 octane? I know they say in a street car if your car requires 87 you waste your money running 93, that hi test just has more resistance to detonation because it burns slower. But with 16-18 degrees timing that I think people run I would think we would get detonation.

Qik Nip Verified Driver Made Donation to Website Series Champ
Loose Member '09 & '10 Great Lakes Regional Points Champion

Region: Cincinnati Great Lakes
Car #: 60
Year : 1990
Posts: 1487
Status: Offline
Icon 1 posted  Profile for Qik Nip     Edit/Delete Post  Report this post to a Moderator

Bump (because I want to know too)

--------------------
Fortune Cookie Racing SM 60
Directions for use: Race, Rumple, Repair ... Repeat!

oem steve
Member

Region: South East
Car #: #92
Year : 91
Posts: 189
Status: Offline
Icon 1 posted  Profile for oem steve     Edit/Delete Post  Report this post to a Moderator

wellllllll, the thing is I don't know what the timing is, I just go to the dyno play with the timing and fuel curve, I do need to put a light on it and see exactly what it is for future reference though as it is now I just marked my cam sensor in case I have to remove it at the track.

--------------------
email: standrewsexpress@bellsouth.net
visit us at http://www.standrewsexpress.com

Under powered and under driven

cintibob
Member

Region: cfr
Car #: 13
Year : 1990
Posts: 105
Status: Offline
Icon 1 posted  Profile for cintibob     Edit/Delete Post  Report this post to a Moderator

OK then I am making an assumption that you are running in I.T. or adjusting a little with the afm for SM. oem If you are adjusting fuel curve what is the ratio in the upper rpm? 12.1 13.1 11.5 Mine is near 11.5 to 12.1 I have heard some people adjusting the CAS where the notch or ledge is even with some ledge on head beside it.

oem steve
Member

Region: South East
Car #: #92
Year : 91
Posts: 189
Status: Offline
Icon 1 posted  Profile for oem steve     Edit/Delete Post  Report this post to a Moderator

I purchased an AFM from an engine builder and it runs pretty consistent at 13-1 across the RPM range. the dyno guy pulls the O2 sensor out of the back of the exhaust manifold and taps in there for the air fuel mix sensor. I loosen the CAS and adjust it either advance or retard after you get the AFM running correctly. My original AFM ran very lean (about 14-1)up until about 6200 rpm and then it went to 13-1 where it made its peak HP numbers such as they are. then went fat down to about 12-1.

--------------------
email: standrewsexpress@bellsouth.net
visit us at http://www.standrewsexpress.com

Under powered and under driven

cintibob
Member

Region: cfr
Car #: 13
Year : 1990
Posts: 105
Status: Offline
Icon 1 posted  Profile for cintibob     Edit/Delete Post  Report this post to a Moderator

Well I guess I am going to go back to the dyno and see if I get a difference with 87 non ethanol gas. I have 2 spare AFM's one is stock and one is adjusted 3 clicks richer along with the one that has been tuned by a local mechanic. I was told by a mechanic at the local SCCA meeting ethanol can make more power if the afr is set richer and change the fuel filter more often. He had no idea if 87 or 93 is best for SM he runs ita so he has more compression and runs 93 octane. I was hoping more people would chime in on if they run 87 or 93 octane.

oem steve
Member

Region: South East
Car #: #92
Year : 91
Posts: 189
Status: Offline
Icon 1 posted  Profile for oem steve     Edit/Delete Post  Report this post to a Moderator

I don't think you will see much of a difference on the dyno but you won't have to spend as much for the gas.

--------------------
email: standrewsexpress@bellsouth.net
visit us at http://www.standrewsexpress.com

Under powered and under driven

Brandon F. Verified Driver
Member

Region: NNJR
Car #: 48
Year : 1996
Posts: 191
Status: Offline
Icon 1 posted  Profile for Brandon F.     Edit/Delete Post  Report this post to a Moderator

So, for all of us 94-97 1.8L owners, where does that leave us in regards to octane?

[Razz]

I run the 93 in mine as I'm leaning on experience with the 2.0L DOHC Neon engine that required the hi-test for the 150HP rating. Figuring the 1.8's would appreciate the knock resistance and not pull timing at higher RPMs.

TR6
Member

Region: Southwest
Car #: 500
Year : 2002
Posts: 179
Status: Offline
Icon 1 posted  Profile for TR6     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Brandon F.:
So, for all of us 94-97 1.8L owners, where does that leave us in regards to octane?

I have the same question for my 2002. I've been running 93 in it just to be safe.

--------------------
Greg H.
2002 red Miata #500
Denton, Texas

cintibob
Member

Region: cfr
Car #: 13
Year : 1990
Posts: 105
Status: Offline
Icon 1 posted  Profile for cintibob     Edit/Delete Post  Report this post to a Moderator

I would say it depends, weather you have the aluim. rad. and water temps. in summer stay under the 200 magic point and how much timing your advanced. Put some 87 in for practice and Qualifying and see how it runs for you. If the car new required to run 87 and your not running in I.T. and other guys are running it in under 97 cars should be OK. I am going to try it on the dyno.

[ 03-10-2010, 10:56 AM: Message edited by: cintibob ]

   

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic | Subscribe To Topic
Hop To: