How to get my MPH back?

[93Rubie]

Ok, so last fall at the drag strip I was running in the 108 MPH range with my trap speeds running 93 Sunoco fuel. Both of the stations in my town closed this past march. In the spring I ran the car and only got 103 MPH. I figured old, Sunoco Fuel w/stabil just was not cutting it. So I used come BP for a while to get the car used to it. Ran again this summer and got 103 MPH. Hmm....so I switched to Exxon which is "supposedly" Top Tier fuel and today I managed to 99-101 MPH.

Last fall I did not have any wheel spin with crappy 60 foots, today I had NO will spin with much better 60 foots. Practice is a good thing, so that takes that out of the equation. As I recall last fall the car pulled noticeably harder on the top end of the track and at higher RPMs. Conditions when I have ran today where similar to last fall, both other times this year where a little warmer but not much. Coolant temps seem to make no difference as I note these and write them down on every pass. Hot or cooler same trap speeds.

Now the BP and Exxon stations probaly do NOT go through much 92/93 Octane so....that being said, maybe I should switch back to crappy Sheetz gas because maybe it is fresher. I had 105MPH traps in the heat of the summer of 2010 with Sheetz has. 92 Octane is what it is rated as.

The only other gas stations in my area are Keystone-gasoline quality unknown, and Kwik Fill same as Sheetz.
There is a Sunoco station 13 miles away in area I rarely go. Who knows if anyone uses the High test stuff there???

My question is what to do about this. I suspect I am getting spark knock and I am getting the timing pulled out and it is killing my HP. I don't have a "tuning and data logging equipment" but I do have a scan tool with a record function. Might be hard to use at the strip however.

I do not like the idea of using Octane Boosters they have some not so good side effects. What to do, go back to Sheetz gas???

On the positive side my Corvette and I are VERY consistent. From 8 passes I got anywhere from a 13.72 to 13.63. That is a deviation of only .09!!!! 60 foots improved from 2.13-2.04. Very smooth 5K launches with NO wheel spin, only slipped clutch for maybe 30 ft TOPS. I'm not really sure how much happens really fast, obviously. Heck, when I actually paid attention to the light the one run, I got a .0414. My previous best is a 13.50 at 103.3MPH w/2.12 60 foot. If I get the 2.04 60 foot with the 108 trap=ET in the 13.3-13.2 range is VERY likely. So you can see why I want my HP back. FYI, I have a total of 25 passes on the car, I think I'm doing ok, but I want to do better the car has it, we just need to find it.

The only other idea I had is 18 year old valve springs+lots of WOT operation since my purchase of the car=weak valve springs=poor top end.

Any ideas.....

 

[1963SS]

You're going to have to figure a way to "record" some data or do some data logging. A laptop, a cable and some free software and you will know if it's fuel related or not. There's not much sense in just guessing. The laptop and cable are fun for troubleshooting also. Once you have the set up you'll wonder how you ever did without it.

 

[boomdriver]

yep...I agree with 1963SS....you need to record whats happening and study it.

IF the ECM is getting some knock signals it will show up. Question is, why and whats causing that?
A stock motor should not rattle with 92oct fuel even at hi-temps. You could start by doing the basics...clean and test EGR, timing, plug wires for grounding or crossing, air filter...the simple stuff.

I battled strong knock for months one time. Made me crazy and went thru all kinds of grief trying to figure out why and how...
Ended up being the brand new accel wires. Threw those away and reinstalled the old Delcos and the problem went away. Lesson...knock can come from lots of places. If your timing is retarding as result of a mild knock there are lots of potential places to investigate. The fuel and where you buy it is just coincidence. Gas is gas. Chemically one brand only differs by the small amount of additives they ( whatever brand) use as the marketing hook...some have benefits, some may not. Bottom line is the gasoline is the exact same thing as the other station sells because Sonoco crude oil yeilds the same end result as Texaco crude oil. Its Gasoline with whatever additives they throw in to slow the combustion and label it as 92 or 106 oct or whatever its supposed to be.
ALL gasoline starts out the same.
EX: back in the 50's when all gas was pretty much 85 oct avg, hot rodders would throw in a handful of moth balls to get a boost in octane and get a bump in performance. Thats basically whats done today (except ethylene is used not napthalene--hence the term "ethyl"=hi-test gas) except its done at the refinery or bulk depot instead of the burger stand. The gas is the same...one tankfull might have more mothballs than the next, BUT the rated level has to be the same from the pump due to Federal regulation and EPA regs that did'nt exist in 1950. Point being, all gas of the same grade in an area is the same gas and probably came from the same depot. Different labels and brand names.

BTW....mothballs don;t help much now because most pump gas has a higher oct rating than the mix of napthalene and gasoline. Xylene does work well because its got an oct of 117 but blending it can get expensive real quick...A qt from home depot is around $6...so enough home brew fuel would cost lots more than good Av-gas or Trick-Gas that sells for around $7 a gallon.
Got way off course here, but the subject of home brew gas and octane is actually kinda interesting. Do a google search on home brew gas. Some interesting stuff out there..

You could use the xylene to up the octane temporarily to see if that made a difference or not...

 

[gmjunkie]

My guess is your experiencing the Ill effects of Corn Cob Fuel!~!!

Don't matter what Major Brand or Grade anymore,All of them have at least 10% or more Corn Cobs!~!!

I've even been noticing the difference in the smell of gas in the last 3-4 years,it's getting where it very much smells like Grand Dads finest Corn Liquor!~!!

 

[boomdriver]

My guess is your experiencing the Ill effects of Corn Cob Fuel!~!!

Don't matter what Major Brand or Grade anymore,All of them have at least 10% or more Corn Cobs!~!!

I've even been noticing the difference in the smell of gas in the last 3-4 years,it's getting where it very much smells like Grand Dads finest Corn Liquor!~!!

yeah......it burns just as well, just don;t taste quite as good !

 

[Hib Halverson]

There are two simple solutions.

First, get a scan tester which takes data and look at your knock retard numbers.

Second, mix 1:3 100-oct unleaded racing gasoline to super unleaded pump gas and see of your mile-an-hour returns.

That said, the difference between 93 and 92 oct ain't much on the track. I'd be surprised if going down one point in octane lost you 5 mph.

When was the last time you replaced the fuel filter? When was the last time you cleaned or replaced the air filter?

 

[6 Shooter]

Back in the day...

​

 

[1963SS]

[h=2]Back in the day...[/h]

Heck, I live in eastern Kentucky. That's not "Back in the day". It looks like my family reunion last year. Ya' gotta problem with that?

 

[boomdriver]

Heck, I live in eastern Kentucky. That's not "Back in the day". It looks like my family reunion last year. Ya' gotta problem with that?

 

[93Rubie]

I appreciate all the feed back.

Yes, I am aware of the ethonal, the Sunoco gas had it too so I do not think that is a factor.
Could the "freshness" of the fuel be a factor? IS old stale gas lose its octane? Who knows how long some of the higher octane stuff has been sitting in the tanks in the ground?

Air filter is K&N, cleaned last year only maybe 4K max. since. Fuel filter was changed in May of 09. Maybe 8K on it.


I never had these issues with the Sunoco fuel. BP, Exxon, yes...Sheetz gas was ok, probably fresher but little additives in that fuel.

Hib, I figured you would recommend some mix of race fuel. I can get it around here but I'll drive (God only knows, I cannot find any with a internet search) miles to get it. Might be better to get myself a 55 gallon drum of the stuff and a pump. Then I can use it every tank full when I'm close to empty and mix with pump gas.

Also, unlike fuel trims which take some time to adjust, I know for a fact if the ECM sees knock it pulls timing right now! How long does it take to get it back? Fuel trims take some driving to get the relearn done.

I Should be at the track again next Saturday and I'll take along my scan tool, get it set up to record and I can watch the knock counts after I run.

Anything I can do that WONT kill my CATS to increase octane of the crap Exxon gas in my tank? It is pretty full, I only got 61 miles on it. I average yesterday 17 miles to a gallon (I made 8 passes). So I only burnt 3.5 gallons.

 

[93Rubie]

Update!!!

I got the Corvette out tonight and took my scan tool along. Warmed it up good every looked good readings wise. I can tell you this the car does not like to start when hooked to a scan tool, cranks a lot. Other than that fine.

Monitoring knock retard, knock sense, and ignition timing, I ran it up through the gears to 90MPH up hill. I recorded while I did this.
I got ZERO knock retard and knock sense. Ignition timing varied between 35 and 37, which seemed about right to me. I bet it could stand a bit more but that seems ok. I drove the car some more and did this again in a different spot with the same result.

I think my Exxon gas is fine, and the car ran very strong. Pulled hard all the way to redline. Never felt flat. This got me to thinking, what was different on Saturday? Air temp was about the same at around 60. Air was dry. Hmmm....I know it was WAY windy. I have ALWAYS left the hood up before between runs to let it cool down better. Not last Saturday it might have got ripped off. I am willing to bet I was not getting full timing due to HIGH intake air temp readings. Keep in mind I was the first car in line for street cars. So I started the car idled maybe 1 to 2 minutes at most, did burn out, then ran. So NO time to let the intake air cool down at all. I am willing to bet this is what happened.

Only one way to tell for sure, go next Saturday and leave the darn hood up. Hopefully, less wind. If it was the gas it should have showed itself tonight but it did not.

I think my real problem is the loose nut behind the wheel...:L:ugh

 

[93Rubie]

Track Update!!!

The MPH's are back, less underhood heat and wind this time. Very cool 55ish. Track was slick until rubber got layed down. I spun something fierce on my 1st two passes in the right lane.

I managed to blow the doors off a new Subaru WRX twice on my BAD passes, those cars are supposed to be mid 13' second cars. I manged to 60 foot better spinning than he did in a AWD car???? I hooked the next pass, it was over before it began. He was stuck in the mid 14's then he left. How is that for a 18 year old car....hehehe.

When I didn't spin or miss a shift (sigh) trap speed ranged from 102-106.53, out of 8 passes 5 where in this area, 4 of which where 104-106.53.

New best ET 13.48@ 106.53. New Best 60 foot (2.01) and 1/8th mile (8.70) on the same pass, then I missed 4th at the end of the track. :ugh &*#((@!!!!(#*#@. (SIGH.....)

60 foots ranged from 2.01-2.09, with the exception of the 2 runs I spun a LOT. So that is much better than ever. I ran a total of 16 passes the last two saturday's. Total of 33 passes on the car so far, in my ownership. There is more there...I just need to find it.

Here is a comparison I ran a new Challenger with a tune on it, guy could drive too...he ran the follows 60 foot 1.91 1/8th 8.45 @82 1/4 13.19 @104.53. I got the HP and the speed, I need the 60 foot a tenth faster, heck I am launching at 5K now and slipping the clutch for maybe 10-20 feet and getting no wheel spin. I think a tenth is best case all I would get out of the car as it sits. IDK???

Car comes out of the hole like this very smooth, RPM's drop as I engage clutch but I feed throttle at the same time, when clutch is fully engaged I am at WOT. I did it perfect (pretty much on the 2.01 60 foot pass). I'm committing how it felt and sounded to memory. No jerkiness just a smooth rush of acceleration.

All in all not too bad for just a C4 LT1 ZF6. I saw a C5 auto run 13.90....:eyerole