STUPID RULES

#1

Pardon me while I vent my frustration with the lack of an adjustable fuel pressure regulator. Over two days I spent 4 hours on the dyno trying to get Wayne Garner’s JUNK YARD motor rich enough to stay together The final dyno sheet is below. To get here, this is what I had to do:

7 ECUs

3 AFMs, each one adjusted and optimized

3 Fuel pressure regulators

About 25 dyno pulls

and I’m still damn unhappy with the trace. The motor is too lean. For less than $150 an Aeromotive FPR can be installed in the fuel rail return line…no other modifications necessary, and the FAR can be adjusted to a safe number. Not allowing the adjustable FPR is false economy because it sure cost more than $150 to get the chart below. Chuck

#2

You are not wrong… I’d support a rule change, but I also secretly hope we’ll eventually allow headers, ECU chips and 4.10’s so maybe I am not the right person for input here.

#3

yawn. :wink:

#4

what would make this particular engine run so lean? Isn’t raising the FP a bandaid for another issue?
(I’m curious)
thanks,
bruce

#5

This motor is not “so lean”. From what I have seen, it is a normal street tune. Perhaps for shorter tracks where the car does not see WOT for 15+ seconds at a time as it does here in the South East, this tune is safe. Not here.

With all inputs replaced or checked to the ECU, fuel pressure would not be a crutch. The motor is operating exactly like designed as a street car, not a race car. And per the rules, what I did on the dyno is the only way to change/correct the mixture.

I understand the intent of the rules is to limit modifications to limit costs, but this is just false economy as the same thing can be accomplished for much less money without improving performance. Chuck

#6

Is this motor (or engine if you are Moberg) really running lean? The scale is pretty tight but it looks like it runs 12.8-13.8 in our race-engine-speed range.

If stoich is 14.7 why do you think 1 point below that is lean?

I only have one data point - my motor that showed 13.6-14.7 on the dyno last July. Since nothing could legally be changed to affect it, I’ve been running the h3ll out of it.

Besides, the rocker arms fail way before you melt a piston.:wink:

#7

Oxygen sensor on or unconnected? Did you try it both ways?

RP

#8

O2 sensor on the motor working and is connected, as the original ECU would never come out of closed loop…hence AFR over 14.5 the complete run. O2 sensor is bypassed at WOT after temp is reached.

Ask any engine/motor builder: in a race motor, 14.7 will melt pistons…13.5 is better, but for best longevity, 12.8 is the number you want. Even with an adjustable FPR, you will be slightly rich at 5500, but so what…every where else would be right. Chuck

#9

cwbaader wrote:

I appreciate threads like this. I always feel like I learn something. Like how little I know.

Are you measuring exhaust gas temps? Seems like AFR is a guide (as far as if you are close to burning an exhaust valve or a piston) but EGT is the critical measurement as far as damaging the motor is concerned.

As far as making maximum power, the experts agree AFR should be lower. But the argument at hand is whether we are going to melt motors with the stock setup.

Also, you say a “race motor” will melt at 14.7. Just because you put an M20 on track doesn’t make it a race motor, does it? :wink: Does compression ratio have an impact on EGTs (e.g. higher compression ratio yields higher EGT at the same AFR)? When I think “race motor” I think high compression, high rpm, race gas, etc. My hope is a good old M20 on 92/93 octane pump gas at 13-14 AFR puts out exhaust gas temps that are well within what the motor can handle for 2-3 seasons.

Granted, with an adjustable FPR we could all turn up the wick and make maximum power… Especially with those pesky intake leaks. :wink:

#10

I would argue that any motor in any car that you flog around a race track is a race motor. In this case we are talking about cars designed for street duty where extended operation at the top of the rpm band just doesn’t occur.

We are racing these cars and are stuck with a "street tune’, which is good for emissions control and fuel economy. But not so good for engine longevity. And other than swapping out all kinds of parts there is no way to compensate for an engine and management system whose tolerances all happen to add up in the wrong direction. It seems to me that there should be a provision in the rules for a way to run the engine a bit richer than stock. A $150 adjustable FPR seems to be a pretty cheap solution in comparison to a a massive parts swap or head refresh or engine rebuild every year or every other year.

#11

Race engines, street engines…aside from stupidity I’ve yet to blowed-up a motor in the 6 years and three cars worth of racing.
My vote, leave the rules set alone so we’re not out chasing the latest part that doesn’t matter.

Key emphasis on “aside from stupidity.”

What does matter is the nut behind the wheel. Yes, I, too need lessons from the Skeen. Someday when I’ve got the time I’ll give the coaching thing a try. Till then I’m resolved to be a moving chicane.

RP

Yes, like Steve, I,m learning stuff about oxyger sensor performance that I did not know.

#12

Robert, you don’t count…I know what you have done to your motors!!! (and it’s not pretty):laugh: :laugh: :laugh:

Exhaust gas temps…are dependent on motor specific output…the more horsepower, the richer you must run (to a point) to maintain acceptable EGTs. Until someone actually monitors EGTs in a race situation on a Spec E30, we are all in the dark. I can tell you this, however. Allen’s car was lean enough to melt the high temp tubing from the exhaust pipe to the dyno O2 sample port…twice. We ended up with just over 5 feet of copper tubing connecting the two.

Another thing to consider…is everyone running stock heat range plugs? Is so, WHY:woohoo: There are racing plugs out there much cheaper than the Bosch most run…exhaple: Autolite AR53,a true racing plug a heat range or so colder than the stock…you can call that “insurance”. Chuck

#13

cwbaader wrote:

Finally we agree on something. :laugh: Kidding. I do appreciate you entertaining my novice questions.

Holy crap! Was the header glowing red?

Do you think the extra tubing allowed for any air to be drawn in leading to a false lean reading?

Again plumbing the depths of my ignorance, but I thought you wanted the hottest plug you could get shy of having pre-ignition issues.

#14

Steve, in a motor that is running lean…NO!!! If you are already running lean, you need to remove as much heat as possible from the combustion chamber to save your pistons. CB

#15

Steve D wrote:

Hotter plugs are designed to have a higher temp then colder plugs. That is to say hotter plugs get hotter. The threaded portion of the plug conducts heat from the chamber. Hot plugs have an insulator design that makes it easy for heat to move from the plug’s threads to it’s electrode. Cold plugs have an insulator design that makes it harder for the heat to move from the plug’s threads to the plug’s electrode. Therefore cold plugs don’t get as hot.

5 secs looking at a diagram of hot and cold plugs will make that stuff clear. What I don’t understand tho, is why. What difference does it make and why?

#16

Ranger wrote:
Therefore cold plugs don’t get as hot.

[/quote]

Oh…now I understand. :laugh:

#17

cwbaader wrote:

Lemme get this straight. You are essentially saying the spark plug acts as a heat sink to lower exhaust gas temps, right?

My novice understanding of spark plug “heat” ranges is that there is a variance to affect the ignition of the air-fuel mixture. That “heat” range affects when the ignition of air-fuel happens (i.e. making sure it does not happen before the spark occurs), not the temperature inside the cylinder.

If your thesis (that spark plug heat range affects EGT to a material enough extent that it prevents burning a piston or valve) is correct, then switching plugs on the dyno would yield a measurable drop in EGT.

I just can’t buy that.

PS - The amount of heat the spark plug transmits (burning air-fuel > electrode > threads > head) to the head has got to be infinitessimally small compared to the heat transferred from the air-fuel mixture directly to the head.

#18

[quote]Ranger wrote:
…Hot plugs have an insulator design that makes it easy for heat to move from the plug’s threads to it’s electrode. Cold plugs have an insulator design that makes it harder for the heat to move from the plug’s threads to the plug’s electrode…[/quote]

I think you’ve got the right idea, but the heat flow direction is backwards. The heat is actually moving away from the electrode.

http://www.howstuffworks.com/ignition-system2.htm

Matt

#19

Matt H. wrote:

[quote][quote]Ranger wrote:
…Hot plugs have an insulator design that makes it easy for heat to move from the plug’s threads to it’s electrode. Cold plugs have an insulator design that makes it harder for the heat to move from the plug’s threads to the plug’s electrode…[/quote]

I think you’ve got the right idea, but the heat flow direction is backwards. The heat is actually moving away from the electrode.

http://www.howstuffworks.com/ignition-system2.htm

Matt[/quote]
Good catch, thx. So hot plugs run hotter not because they absorb more heat from the hot metal chamber, but because they dump less heat to the “cooler” chamber.

Steve, I agree that the primary reason for cooler plugs seems to be to ensure that a hot plug doesn’t cause pre-ignition, but Chuck raises an interesting point.

Given Matt’s correction on heat flow, a cooler plug will definately suck more heat of out the exhaust gases and transfer it to the coolant, even if it’s not a helova lot. A single piston combustion cycle doesn’t create a ton of heat. Consider how long it takes to warm up an engine. If a cooler plug is constantly pulling hundred calories/min out of the chamber, it ought to make a measurable difference in exhaust temps. Not a big difference, but measurable.

A lump of metal at 10deg above ambient takes a long time to cool a couple degrees. A small amount of gasous material at a very high temp will cool a couple degrees in the blink of an eye.

#20

Ok. It might be just me but it is just wierd watching you guys talk about my car. Its like talking about someone while they are still in the room. :laugh: Maybe its just me but it comes across as strange. I can’t thank Chuck enough for everything he has done for my Father and I. He has a vast amount of knowledge and is always willing to share and help. Look forward to seeing how all the changes we have done to the car will work at PBOC this weekend even if it is an 80% chance of rain.