Australian Corvettes Association

PhantomVette · Posted: Wed Dec 02, 2009 6:44 pm Post subject: Petrol

Hey just a quick question!

can the vette handle 98 ron from BP?
or is 95 the highest it should have!
91 is what they suggest!

Just being cautious! cheers

Winfield RED · Posted: Wed Dec 02, 2009 8:17 pm Post subject:

Mate i wouldnt bother with 98 on a stock L98, and 91 RON is not what they suggest, 91 PON is what they suggest.

If you were to tune the car for 98 octane fuel then youd be pretty near forced to use it every fill, but with the way it all is now, 95 BP is what i strongly recomend you use.
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"Trends may come and go, but Mercedes Benz will always be...."

WA Vetter · Posted: Wed Dec 02, 2009 11:10 pm Post subject:

If I wanna get a bit extra outta the car at the drags is it worth running, will it run with a tank of av gas Confused

Is all av gas the same grade ??
does it smell different out the exhaust and wot sorts side effects will I have, i can get it from work
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If its not fun, its not worth doing ,,,

australi · Posted: Thu Dec 03, 2009 11:18 am Post subject: Re: Petrol

steves87 · Posted: Thu Dec 03, 2009 2:45 pm Post subject:

I only use ultimate, car seems to like it... supposedly a much cleaner fuel and is garanteed if it harms to your engine (and can be proven) my brother inlaw is an engineer who 'makes' it, doesnt seem right to me not to use it Chuckle

PhantomVette · Posted: Thu Dec 03, 2009 6:36 pm Post subject:

steves87 · Posted: Thu Dec 03, 2009 7:02 pm Post subject:

Winfield RED · Posted: Thu Dec 03, 2009 9:13 pm Post subject:

Before we go any further, lets dispell some bullsh--. Higher the octane, the slower the fuel will burn. If it burns too slow, youre just going to piss it out the exhaust. If your spark is not advanced far enough for the higher octane fuel, youre wasting your money on it. Full stop.

australi · Posted: Fri Dec 04, 2009 9:26 am Post subject:

What you say is true, unless we were talking about a carby car, which we're not.
Main answer to the question IMHO is I wouldn't run on 92 myself.
Yes the TPI system will adjust for it and is far less critical than a carby engine, but I still wouldn't.

And my thoroughbred remark was a reference point only - I KNEW YOU would come in on that one and dispell it Toothy Grin

ben73 · Posted: Fri Dec 04, 2009 10:18 am Post subject:

Avgas still has lead in in, even the LL variety.
It will kill your exhaust o2 sensor. You would see no benefit from it anyhow.

Winfield RED · Posted: Fri Dec 04, 2009 7:06 pm Post subject:

PhantomVette · Posted: Fri Dec 04, 2009 9:32 pm Post subject:

Well ok you learn something new everyday thumbs

thanks for saving my money on the rediculously expensive 98 BP! Toothy Grin

Steve87: what ashame, thanks anyway! Toothy Grin

Winfield RED · Posted: Fri Dec 04, 2009 9:45 pm Post subject:

Its not over priced, its well priced, you just dont need it!! thumbs

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"Trends may come and go, but Mercedes Benz will always be...."

australi · Posted: Sat Dec 05, 2009 11:26 am Post subject:

PhantomVette; your call but I'd still use 98 EVERY TIME.
Advance the spark to 8 to 14 degrees BTDC - I saw a difference for the better myself...As do a lot of C4 people I know.
It may run a fraction hotter, but negligable worry.

That's the last of my 2 cents worth - take it or leave it. Impatient

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WA Vetter · Posted: Sat Dec 05, 2009 11:48 am Post subject:

is advance clockwise or anti clockwise, and how many degrees is each mark - will this make it run faster with98 ??
_________________
If its not fun, its not worth doing ,,,

australi · Posted: Sat Dec 05, 2009 11:56 am Post subject:

You'll see the marks with a timing light, each point is 2 degrees.
I found it made mine a bit 'zippier'.

australi · Posted: Sat Dec 05, 2009 12:29 pm Post subject:

The timing mark will appear to move to the left as it's advanced (given the engine turns clockwise from the front).

I also adjusted my throttle position sensor (TPS) slightly to 0.65volts (from standard .54v); that too gave me a slightly better throttle response.

The adjustment sequence I have in our own tech tips link, in our link section, specifically at:
http://www.australiancorvettes.com/docs/Base%20Idle%20Speed%20Adj%20-%20C4.doc

...I'll reproduce the doc below:

australi

Corvette - 350 TPI Engine
L98 engines - 1985 thru 1992: Not applicable for LT1 or LT4 engines.

Setting Base Idle Speed (using 89 GM Helms Manual)

If this has not been done on your car before, the adjusting screw will be covered by a pressed-in plug. It’s located on the driver’s side of the throttle body. Remove this plug by using a small punch. Impact the plug on the side of its face and this will allow its removal.

1. Start the car and let the engine warm up to its operating temperature. (It is suggested that you make sure the timing of the engine is set to specification prior to doing this procedure.) During this step, the engine should be in closed loop operation and all electrical accessories INCLUDING COOLING FANS should be off. Shut off the engine after it is warmed up.

2. Turn ignition switch to ON, but do not start engine. Adjust the Throttle Position Sensor to .54 +/- .08 volts using a digital meter. There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Mid America costing $12), or gently pierce the insulation of the wires with the pointy prongs on your voltmeter. You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. The adjustment is accomplished using a Torx driver and loosening the two screws that hold the TPS to the throttle body. Then rotate the sensor either clockwise or counter clockwise (with the ignition on and engine not running) to obtain the .54 volt specification. Retighten the two TPS Torx screws to “lock in” the adjustment.

3. With the IAC connected and the ignition “OFF,” insert an Auto Zone tool (free upon request from Auto Zone) into the diagnostic connector (ALDL) terminals “A” to “B.” (These are the upper right two holes in the connector.) This grounds the ECM and places it into the diagnostic mode.

4. Turn the ignition to the “ON” position without starting the engine. Wait 30 seconds before doing step 5. Doing this forces the IAC pintle to the closed position (closes air passage) within the throttle body.

5. With the ignition still in the “ON” position, disconnect the IAC connector at the IAC valve. This action prevents the ECM from controlling the idle speed using the IAC valve.

6. Turn ignition switch off!

7. Remove the Auto Zone tool from the diagnostic connector.

8. Disconnect the timing connector located just behind the left valve cover. This is necessary to prevent the ECM from attempting to adjust the timing as you adjust the idle speed. This will be a brown wire with a white stripe and easily separates using a small screwdriver to raise the locking tab. Failure to do this step will allow the ECM to control the idle and you will not be able to properly adjust the base idle.

9. Start the engine. The idle speed will be really low, and you may have to coax the engine using the gas pedal or your hand and the throttle cable to keep it running. I find it useful to insert a small screwdriver between the end of the idle adjusting screw and the throttle body to keep the car running at this low idle point. HOWEVER, REMOVE THE SMALL SCREWDRIVER BEFORE MAKING THE FINAL IDLE ADJUSTMENT!!!

10. If your car is an automatic, set the parking brake and put the transmission in park. If your car is a manual, leave it in neutral.

11. Adjust the idle speed screw to obtain 425 +/-25 engine rpm. This will require a Torx tool to adjust the idle screw in the throttle body. As you adjust the idle screw to obtain the desire idle speed, you are changing the TPS voltage setting. The TPS will require re-adjustment in step 12. Make sure the cooling fans are not running while you make this adjustment.

12. Shut off the engine, re-connect the IAC and the timing connectors.

13. Turn on the ignition switch and do not start the engine. Reset the TPS to .54 +/-.08 volts as stated in step 2. Turn off engine.

14. Reset the IAC pintle position by:
a. Depress accelerator pedal slightly.
b. Start and run engine for about 5 seconds.
c. Turn off engine for 10 seconds.
d. Start engine and check for proper idle operation.

You are now in adjustment on base idle speed and TPS output. Start the engine. It
may take a few minutes for the car to “catch on” or learn its new settings.

It should be stated that the throttle response from the engine can be increased by using a setting of .62 to .65 volts instead of the .54 specification. If desired, this change should be made after setting the base idle (using .54 volts).

I also set the timing on my 89 350 engine to 8 degrees before top dead center (BTDC). This setting along with the .65 volt TPS setting gives good throttle response. It is very difficult to start the car rolling, as it really wants to take off and run!!!

Revised by Bob Lamb ('samlam') 10/2003 from a tech article written by Lars Grimsrud 10/2001. These changes were required to align the Grimsrud article to the Helms GM manual for an 89 Corvette.

Winfield RED · Posted: Sat Dec 05, 2009 1:02 pm Post subject:

Why would he want to follow the 1989 Helms manual? He has a 1990, and they are NOT the same.

If you dont know exactly what youre doing, dont be f**kin with the timing beyond stock specs. Detonation kills.

Secondly, advancing the timing SHOULD NOT make it run hotter, it should run the same or cooler unless youve gone too far.

Thirdly, you shouldnt be advancing the spark by advancing base timing unless youre ripping a new chip to tell the ECM where you have the base timing set, cause it needs to know or it wont run right. The only way you should be advancing spark on a computer controlled engine is by changing the spark timing maps in the ECM bin file, and ripping a new chip.

Forthly, the setting for the base TPS voltage is 0.54 volts for a good reason, and if it is set to 0.65volts, youre telling the ECM the throttle is not shut. The throttle position has a bearing on a few different parameters, and should be set PROPERLY, and within the spec listed in the factory manual.

Fifthly, i dont think the TPS on a 1990 can be adjusted anyway, and the ECM will automatically calibrate it each start up cycle, and will set the base figure at the lowest figure it sees. No sense playing with it, just leave it alone. Its not going to improve your performance anyway, i dont care what anyone else tells you.

If you want to do this, you do it right, or you dont touch things like this. Later on down the track if you do what is stated to you above, youll come across problems that can be very difficult to track down, especially if you dont know the full system and how it works and youve only changed part of something that should be done as a complete setup.
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"Trends may come and go, but Mercedes Benz will always be...."

australi · Posted: Sat Dec 05, 2009 1:44 pm Post subject:

The proceedure worked fine for me!

"the setting for the base TPS voltage is 0.54 volts for a good reason, and if it is set to 0.65volts, youre telling the ECM the throttle is not shut."

Correct; therefore allowing a more advantageous mixture.

Winfield RED · Posted: Sat Dec 05, 2009 2:48 pm Post subject:

Mate read what i wrote again word for word, the car he has is a 1990, not an 85, and not an 89, so NO it wont work that way. Ive told you before they are NOT the same, and procedures for one wont always work on the other. In order to advise people on improving performance, you must first understand how the system works, and youve indicated that you do not.

And no, telling the ECM you have the throttle slightly open WONT give you a more advantagous mixture at all, where do you get that bullsh-- from? That isnt how it works at all. The O2 sensor will be telling the ECM what it needs to do to keep the A/F ratio where it belongs with both those settings, so the mixture should be no different, providing your engine is running correctly.

What you are posting up is something you dont understand cause you dont know what effect those changes have on things, and you made that clear by the reply you just gave me. Not only that, its totally irrelevant to the car he owns anyway.

I dont think its a good idea for you to advise people to go ahead and do these jobs when you dont know enough about the system yourself without at least telling them there could be serious consequences as a result of following your procedures up to and including engine failure. Advising someone to increase their base timing to 14 degrees instead of 6 or 8 is recipe for potential disaster.
_________________
"Trends may come and go, but Mercedes Benz will always be...."

rayngay · Posted: Sat Dec 05, 2009 3:20 pm Post subject:

Casey is right, early 80's to 89 run MAF Sensor, 1990 runs MAT Sensor, it has a TPS that is not ajustable. Works different to MAF ,MAT computer does mass calculations to ajust itself.

australi · Posted: Sat Dec 05, 2009 5:30 pm Post subject:

Engine failure horse sh*t.
I merely pasted it as it's written.
Yes I KNOW MAF & MAT are different! (not my fault the year range in the title is incorrect)

You keep saying casey, the system (rightly) does alter according to input from sensors etc; so now you're going back on what you say?

I'm not the dumb sh*t you like to try and make out that I am mate,
and if you think for one second I made this forum for people like you to try and take the piss out of me; you're sadly mistaken!

I'm not telling anyone to do anything; merely saying what I did and how it benefitted my throttle response.

Anyway; frankly I've had enough of this sh*t.

Winfield RED · Posted: Sat Dec 05, 2009 8:07 pm Post subject:

Mate stop claiming to know things you dont, cause ill keep correcting you every time.

The year range in the title of the sh*t you posted is spot on, This man owns a 1990 Corvette, which is a MAP sensor car, 85 to 89 is a MAF sensor car. Got nothing to do with that anyway, that was not written by anyone that knows the system well enough to know the ramifications of setting items such as the TPS out of factory spec. I do.

Where did i go back on what i say? Show me, cause i dont see where i did. You dont know how the system works, and that is clear.

Im not here to make you look a fool, by telling people you know what youre talking about when youre wrong youre doing that well enough on your own. I DO know enough about how it works to clearly see you do not.

If youve had enough, then i strongly suggest you stop giving advice in areas youre not well educated on, or ban me from the forum so i dont come along and point out the errors and the possible result of doing what you suggest.

Better take a good look at what youre typing up, cause i find it hard to believe anyone is going to see ive gone back on what i originally said, cause i didnt, and i stick by what i say about how it works. What you say is straight up wrong, cause youre saying mixtures change with TPS settings. WRONG. Doesnt work like that, and there in lies the floor in your theory.

It may very well have benifitted your throttle response, but not cause of mixutes, it WILL be cause your tune is not set as it should be, and the correct way to fox that is to have a new chip done for it, not to adjust the TPS setting out of spec.

Do things right, or dont bother at all. Dont post up things that are either not relevant to a car in question, or potentially damaging to an engine. Advancing the spark by 6 degrees across the board is insanity and not the right way to go about things.
_________________
"Trends may come and go, but Mercedes Benz will always be...."

WA Vetter · Posted: Sun Dec 06, 2009 12:12 am Post subject:

australi · Posted: Sun Dec 06, 2009 9:42 am Post subject:

Ok winnie; so now you're saying that 3 of us, including the guys who wrote the article, don't know what we're talking about? lol

Good thing we all have you here then - the ONLY bloke that knows how everything in the world works; the rest of us are completely wrong Razz

I KNOW how the TPI system works mate - I know it quite thoroughly and it aint rocket science.

As for banning you - why would I do that??
All you're doing is voicing your opinion - just that you manage to do so in an offensive manner is all; that's what grates upon us...
cheers

PS; it was JB who first told me that he regularly tunes his cars to up to 14'BTDC - he does nothing but fix and tune corvettes every day for a living...Guess he doesn't know how they work either then... Chuckle

Winfield RED · Posted: Sun Dec 06, 2009 11:27 am Post subject:

australi · Posted: Sun Dec 06, 2009 11:32 am Post subject:

He's certainly no hero of mine!
I was merely telling you what he told ME! And he made no reference to adjusting anything else; we were talking about base timing.

I am in no way saying that adjusting the map of the ECM is not THE correct way to do things. Just that I have and would without hesitation again, adjust to my current 10'BTDC AND adjust the TPS as I've done...Better throttle response, bit more oomph. That's it.

I have no desire to continue this 'debate'...I'm trying to have a good day today cheers

australi · Posted: Sun Dec 06, 2009 11:36 am Post subject:

Check your email Cool

Winfield RED · Posted: Sun Dec 06, 2009 11:50 am Post subject: