What would be a better gage to have

Dirtracer 619

Well-Known Member
I have fuel injection on my motor, what would be a better gage to have
Fuel pressure or air fuel ratio. Either one is another the high side of $200 bucks so if you had to choose

Note I have a test fuel pressure gage but it's only for testing. No baffle so can't run with it out in the dirt
Thanks for any opinions
 

mgobaja

Well-Known Member
So with your two options, can you adjust both in the field, during a race ? Fuel pressure - yes if an adjustable regulator is used. A/F Ratio ?
 
^^^ A/F ratios were adjustable on the Simple Digital System's FI folks were running on air-cooled motors at least two decades ago. I remember riding in a SCORE-legal Class 5 that had a knob to enrichen the mixture if needed in uphill washes, then lean it out for more power.

OP: do you have that function on-the-fly?
 

Dirtracer 619

Well-Known Member
No i have a basic old school OBD1. Adjustable regulator Aeromotive 750 pump. Had some random fuel issues. Like shutting off in the middle of a race like its out of gas. Wont start Until you shut the battery switch off when you turn it back on it will start right back up so I was thinking that might be a relay so I upped the relay 40 amp from 20 to see if that helps also it seems like I’m getting excessive cylinder heat I melted the fiberglass wrap on my exhaust pipes and even melted the fiberglass in my muffler water temperatures never got excessively hot though but while I’m down working on this I put in a oil temperature gage to see if I can find out what’s going on otherwise it runs great
 
Do you have a thermostat or other flow reducer in the cooling system? Coolant moving too fast not efficient at removing heat.
 

dzrt performance

Well-Known Member
I have fuel injection on my motor, what would be a better gage to have
Fuel pressure or air fuel ratio. Either one is another the high side of $200 bucks so if you had to choose

Note I have a test fuel pressure gage but it's only for testing. No baffle so can't run with it out in the dirt
Thanks for any opinions
having one versus the other is not an accurate way to measure fuel flow.

for example, you could have steady fuel pressure but still be lean. if you get dirt/contamination in your injectors or filter, this likely wouldn't show any abnormality on a fuel pressure gauge. if your fuel regulator is vacuum referenced, the fuel pressure wont be steady and vary with engine load. 02 gauges don't know about exhaust leaks, sensor to close to the end of the exhaust, or decal fuel cut strategies…..so there may be times it reads lean and yet that is normal.

excessive EGT is often times a sign of poor tuning, specifically too little ignition timing, or possibly excessively rich fuel mixture where the heat is going out the exhaust instead of being used as combustion efficiency (think lost HP).
 

EOR1488

Well-Known Member
Yeah I got both and have been happy with that choice because both have already come in handy. with A/F I have target A/F and actual on there so its pretty apparent if something is going wrong. U could run a heap inline gauge at the TBI if you just need it for basic function.
 

Bert is my name

Well-Known Member
Rich running could be the cause of excessive e.g.t. but late timing will definitely cause it. A/f gauge is useful. But knowing how to read plugs is even more useful. Besides being able to check the fuel ratio. You can check to see if timing is where the engine wants it as well. Hook a vacuum gauge up when timing the engine. Take it to the highest at idle vacuum reading and using a timing light or your laptop.( however you adjust it) back off from that reading by about 2-5 degrees. Then mess with fuel and idle adjustments. Even with computer controls I still use the old school tools when tuning to verify that the computer is doing what it says its doing.
 

jon coleman

Well-Known Member
a fuel psi gauge is real time issue solver when in a loooong sand wash- full load, dyno runs are too short , psi is just fine until the real world stage, one guy in the class i was racing had an issue w fuel cell venting or lack thereof, caused fuel delivery issues.plug readings are best after a Hard coyote wash run.just get to pit right away with least amount of cruzing- ideling, oh, & let those aluminium heads cool before plug reading
 

Bert is my name

Well-Known Member
Put in more pump than you need and regulate the volume and psi down to what you need. Return style systems are less prone to changes in pressure and volume than return less.
 

Dirtracer 619

Well-Known Member
Do you have a thermostat or other flow reducer in the cooling system? Coolant moving too fast not efficient at removing heat.
I do have a stock thermostat in it and a very large Radiator with twin 16" fans and moter runs at the most about 205 -in washes and silt beds most of time down around 190 that why this is all so frustrating.

So I just put in better headers New distributor a msd ignition box I will double check timing and get it ready to go to the Dyno

Thanks for the ideas
 

Dirtracer 619

Well-Known Member
Bert, I have all Aeromotive pump filter and regulator, return type system
Plumbed into stock fuel rails with 36# injectors. The stock fuel rails to my understanding should be good up to 600 hp I am at about 350 ,
Thought about moving to Aeromotive fuel rails but that's a $750 ticket that I'm not sure I need (I will if that's what's needed just not convinced yet)
 

jon coleman

Well-Known Member
oil cooler thermostat run with a drilled out water thermostat 195dgr seemed best, it would still flow ok if it failed, temps at out flow stayed 195 220 max sand wash, mesured at the thermo stat housing.ran straight water w- a jug of red line water wetter.cooling stuff is a bug a boo
 

Dirtracer 619

Well-Known Member
5.0 sbf bored and stroked to 331 cu in

Aeromotive rail mounted adjustable fuel regulator set at 40 psi

I dont think its a water cooling issue
More like fuel timing issues.
 

jon coleman

Well-Known Member
a buddy ' splained once that psi& volume/ flow are different, efi pumps love to push, they Hate to suck, make sure its not trying( efi pump) to pull fuel through pick up/ in line filters, especially up hill and a long way befor ' pushing ' fuel to rail/ regulator
 

PaulW

Well-Known Member
Fuel pressure with sender on the fuel rail on both my EFI off road rigs. Pressure tells a lot. Obviously the sender is downstream of the regulator, so you get warm feelings about pump flow and regulator accuracy. Best of all get a smart gauge that has set points that turn on idiot lights for low and high pressure readings.
 

Bert is my name

Well-Known Member
If it's a serpentine belt drive those pumps are reverse rotation. The old style pump will fit but impeller spins the wrong way.
 
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