260 & fuel setting?

[K-DAWG XB 2003]

OK. I just bought myself a Mercury racing DDT by OTC. I have a a-48 BOX. Figured if I was gonna own a 260 I would need one of these to change the fuel setting. In 95 degree 80% humidity weather where is a good base line number to set it at to start 101, 99?

 

[bruce pitts]

being a DDT will not show 100 i allways set my box on 99 to play if i'm going to make a long hard run i set it on 101

 

[jas638]

i am thinking bout gettin one of those ,please let me know how it works for ya. and what it does and doesnt do. thanks

 

[chad202]

97-99 in the summer and 101-103 in the winter.

 

[BGohr]

A stock 260 should run at 97-98 all the time, the problem with the DDT is it doesn't read even numbers, so if you set it at 97, it could really be 96, 97, or 98

 

[h2oskiier30]

Are the adjustments on the boxes static, or do they float? I ask because the fuel graduations on my A63 has been marked with all the fuel setting numbers using a DDT. I use the markings as my adjustment tool, since I don't own a DDT. If the adjustments aren't static, however, I guess I could be opening myself up for serious problems.

 

[pirogue]

Are the adjustments on the boxes static, or do they float? I ask because the fuel graduations on my A63 has been marked with all the fuel setting numbers using a DDT. I use the markings as my adjustment tool, since I don't own a DDT. If the adjustments aren't static, however, I guess I could be opening myself up for serious problems.

They should remain the same.

 

[allison8503]

Does the DDT show the injector pulse time like the four botton does. If it does couldnt you adjust it by thay?

 

[Volatile]

The air temp sensor will adjust for temperature changes, in fact it usually changes TOO far from our testing. The system does NOT adjust to sea level , barometric pressure or humidity to name a few things. There are many factors to consider, such as 1) are you running full out runs or sprint racing & cruising around the lake, as the ecu tends to be slightly lean in the 4500-5500 range if you cruise a lot. 2) How heavy is your rig and how tall is your prop? Engines pump more air under load. Whereas you can run the box leaner with a small pitch , swapping to a high pitch means more fuel should be added to the mix.
Short drags in the summer with high humidity or altitude with a small pitch may mean 95 on the box for a stock 260 / A48. 3) All motors have some variation. Older sets of injectors will run richer, as the pintle springs are softer from use. Fuel pressure reg's can vary and so can the driver SCR's in the ECU. Even voltage to the box with effect your setting. Determine what you are going to run for a setup, make some passes or run your game and run a #8 or 9 series electrode style plug. The #9 will read closer to piston color than a #8. Check the plugs often and kill the motor at high rpm, not after idling. A 98 setting on one rig may run too rich on another combination of factors.

 

[pirogue]

The air temp sensor will adjust for temperature changes, in fact it usually changes TOO far from our testing. The system does NOT adjust to sea level , barometric pressure or humidity to name a few things. There are many factors to consider, such as 1) are you running full out runs or sprint racing & cruising around the lake, as the ecu tends to be slightly lean in the 4500-5500 range if you cruise a lot. 2) How heavy is your rig and how tall is your prop? Engines pump more air under load. Whereas you can run the box leaner with a small pitch , swapping to a high pitch means more fuel should be added to the mix.
Short drags in the summer with high humidity or altitude with a small pitch may mean 95 on the box for a stock 260 / A48. 3) All motors have some variation. Older sets of injectors will run richer, as the pintle springs are softer from use. Fuel pressure reg's can vary and so can the driver SCR's in the ECU. Even voltage to the box with effect your setting. Determine what you are going to run for a setup, make some passes or run your game and run a #8 or 9 series electrode style plug. The #9 will read closer to piston color than a #8. Check the plugs often and kill the motor at high rpm, not after idling. A 98 setting on one rig may run too rich on another combination of factors.

There is a very good summary Randy! Any more headway this weekend??

 

[K-DAWG XB 2003]

I actually just hooked it up and played with it. I havent adjusted the fuel. Its set on 99 and I figured that was lean enough. I never run light. I always have at least the wife and the dog, cooler full of drinks, anchor, spare prop, some misc tools, that type of stuff. I figure that my missing rpms cant be due to the fuel curve and must be else where. I have never rode in another XB2003 with a 260 so, I dont have anything to compare mine with. But, mine seems to run real strong up till about 6700 to 6800 then it slow to move up to 7400. I havent checked my fuel pressure. Could be a loss of fuel pressure. Once I get finished up with the house which should be the end of this month I'll be able to do some serious testing and tuning. I have always been scared of hooking and not wanting to raise my motor more than it already is. It handles extremely well at the height that it is so, not sure if there is much more to gain by going higher than 1/16 of an inch below. I think I told you an 8th before. But, its a 16th below.

 

[Volatile]

What model fuel pump? Bosch 957, 984 or the little one? Also you may want to try having a chip richened at topend by 5% and see what that does for you. You can swap them easily and always reflash it. I like about 5-8% lean from idle to 2500 / 3000 and then richer from 6500 to 8500 and then leaner at top end after the motor is past it peak volumetric efficiency. You can also try an adjustable reg or use a socket and squash down the standard Bosh 200 to add a few psi. Always do the changes with a SECOND part or item ( chip, reg, prop, etc) so that you can change back if its the wrong direction.

 

[K-DAWG XB 2003]

I bought it (fuel pump)from brucatos, They asked what ecu I had and I told them 11350 with an A-48 chip. It is a 39 psi system. What I really need is to have someone who knows whats up to take a look at it for me........lol

 

[Volatile]

Take it to Mumford. He's in Baxley, GA. Larry Mumford. Or Big Boys Toys nearby.

 

[ziemer]

I bought it (fuel pump)from brucatos, They asked what ecu I had and I told them 11350 with an A-48 chip. It is a 39 psi system. What I really need is to have someone who knows whats up to take a look at it for me........lol

The bigger pump has a longer neck on it, compared to the smaller bosch. Either pump will work with either regulator.

I ran an A-48 for a long time on my 260, but it had a few mods...lake exhaust, rod slots, mild porting, spacer plate and 150 psi heads. With that motor I ran it at 102 all the time.

My current motor is a bone stock 260, with same spacer plate and heads (150 psi) and I run an A-6 at 100 all the time.

With the chit ethanol crap, I don't see the problem with running a little richer 101 ish rather than 98-99.

BTW, be careful on modifying the regulator. I had one that was "squished" too much (didn't know it at the time) and it took me forever to figure out why my motor was so lazy on the bottom end. Ended up that the regulator was letting almost 60 psi of fuel pressure on a 39 psi chip.

 

[chad202]

Bosch makes an adjustable regulator that's great for tuning in an engine.

 

[Volatile]

Yes, the adjustable Bosch will work great and will allow higher pressures. You will need to be sure the model has a vacuum fitting in the adjustment post so that your pressure drops at idle like the model 200 though. There are some Bosch with and some without that are adjustable. A vac. barb can be added to the non vac. style if thats all you can find. A nice investment for under $100. Changing pressure can be read easily on a pressure gauge, whereas changing the ECU setting requires a DDT or 4 button tester.

 

[chad202]

You can do it without DDT or 4-button but u will have to have pyros and know where it needs to be based on spark plug readings. I did it all th time before getting an ACU w/steamwheel.

 

[Volatile]

Yep, thats correct. Plug readings or EGT will work as well, but its nice to know the %age or amount you are leaning or richening. A fuel press. % is easier than over leaning by accident and watching the EGT's. And the digital EGT with recall for highest temp would be the best way yo use an EGT, unless you are extremely familiar with your motor and how fast your pyro's react, how good you are at watching a gauge while you drive topend, etc. All good advice though.