No torque

#1

Just had my car on our shop’s dyno. It made 149hp and ~128ft lbs of torque. It’s a Mustang dyno so those numbers are likely a little low compared to the Dynojet ones NASA uses.

But what’s with that torque gap? I see people posting 150hp / 150 tq all the time. How do I narrow that gap? We did a top end refresh last year, and I’ve only done maybe 4 race weekends since (no testing), so I figured the motor was pretty healthy.

We futzed with the AFM settings and swapped some ECUs. It got me a couple of HP but did nothing to narrow that torque gap. There’s a good size drop around 5500, wonder if that’s related.

#2

These motors make peak torque lower in the RPM range than where they make peak horsepower. I don’t believe the AFM is a utilized sensor at WOT. I would try ECUs and make sure the ECU is getting the correct coolant temp sensor value it is looking for as that is utilized at WOT.

#3

I think Chris is right. DME has 2 triggers to go to open loop. 1) TPS signals WOT or 2) AFM door fully open (400-4500rpm?). At open loop the only sensor the DME apparently listens to is coolant temp.

Note tho that long term fuel trim (LTFT) can get you. This is set by O2 sensor and AFM. If your LTFT is goobered up, say it’s too lean, then when you to WOT it’s still going to be too lean.

That said, I’ve never heard of such a big delta between hp and torque so I don’t have any good ideas. I would contact Jim Levie and Chuck Baader and see what they think. You can track them down via the Members link at left. Also, you should post the dyno result. Be sure that it has F/A info. Dyno results w/o F/A are good for compliance, but they don’t tell you much about what’s going on with engine management.

Ideally, you got the dyno data from the shop and can get the software to create graphs at home. This allows you to zero in on different parts of the curve so you can see more detail.

My bet is that this is simply an artifact of the dyno. I think that there is some consensus that Mustang Dynos read lower then Dynojet dynos. I’ve only been on a Mustang dyno once and it was indeed low. Jeff Retey spent some time on a Mustang dyno recently I think. You might ask him about his experience.

Before you spend a bunch of time and energy on the problem, I’d see how hard it would be to get on a local dynojet dyno that other SpecE30 types have been on. You might find that you don’t have a problem.

#4

A year ago I ran on a dynojet dyno and got 154/144. So already a big delta.

This time I got 149/128, an even bigger delta…granted it was a Mustang dyno.

I’m thinking I might do rings, pistons & whatnot after nationals, but no time to do anything before then.

#5

Doesn’t look like you have AFR readings on that dyno plot. The plot looks pretty normal to me. I would go back to a Dynojet and get good AFR readings on 3 straight runs. That should really tell the story and possibly save the rebuild budget for later.

#6

Need more resolution of F/A curve. The only way it could be that flat is if the sensor wasn’t put in the tail pipe, or if the F/A Y axis # is way too big.

The problem with the torque # is the big drop off at ~4400-5200rpm. That’s an engine management issue, not a “pump” issue. The fact that your engine delivered good peak hp at rpm should indicate that as an air pump your engine is fine.

Your challenge is to mitigate the drop in performance between 4400-5200rpm. The general theory re. what’s going on there is that Bosch found the engine susceptible to knocking in that rpm band and the DME pulls back timing to make the engine less susceptible. To attack this problem I’d research what other folks did because it’s a common problem, and I would get better F/A data. Better means a curve that lets us see what is going on.

We all have a dip in power in this region, but some are worse then others. Yours is particularly bad. The good news is that it looks to be engine management, not the engine.

#7

And bring the data home so you can set up better charts that exactly show what’s going on.

#8

I would take a look at your spark plugs, i changed mine earlier this year and gained 8ft/lbs TQ and no HP haha

#9

I only took that photo. Fuel / air was steady the whole way. Plugs are cheap and easy, and I generally like the cheapest fix so I’ll start there!!

#10

Install a set of Autolite AR53 and gap at about .035". Agree with Scott…get to a DynoJet and get a graph. There is a wealth of knowledge about the DynoJet numbers here. It is not normal for the FA to be constant with the stock ecu. I suspect the rheostat on the throttle body is not signaling WOT and the motor is trying to run on the O2 sensor. Other than the plugs, that would be the first thing I would check.

#11

The mustang is a better dyno and will be 10 to 15% low. It has the option of giving you the same numbers a dynojet would give you. Call the shop you went to and ask them if they can give you the dynojet results.

#12

From the dyno plot, it appears that something is causing your motronic system to pull timing or your cam timing is screwed up. I’d start troubleshooting the Motronic first as it’s most likely.

As already suggested by others, I’m also suspect of your coolant temperature sensor or wiring. If the Motronic doesn’t receive a signal from the CTS, sees extremely low resistance indicating that your coolant temperature is very high, or you simply have an open circuit, it will pull timing and kill your torque. To check, measure the resistance of pin 45 on the DME connector across ground with your engine at ambient temperature. This is the only way to verify wiring and the sensor. With coolant temperature of 68 to 86 degrees F, you should see resistance values of 2500 to 1707 ohms. Higher resistance is better and resistance decreases as coolant temperature rises.

If the CTS and wiring check out, my only other suggestion is cam timing. If retarded, you will lose torque down low and alter peak power. Significant retardation will have a large negative impact on torque while only slightly reducing peak power. This begs the question on your cylinder head thickness which should be 4.909" or greater; this is easy to measure with a caliper or 5" micrometer, but likely tricky in car. Otherwise, you could be off a tooth on the cam gear.

#13

One other thing. What is the history of the motor. Junk yard, with car, rebuilt, timing belt changed, etc?

#14

And bring the data home so you can set up better charts that exactly show what’s going on.[/quote]

Is anyone maintaining a database of these Dynojet run files? I think that would be a good thing to start doing. I have 3 files for my original motor, and 3 files from my Fish motor I would me more than willing to make public.

#15

And bring the data home so you can set up better charts that exactly show what’s going on.[/quote]

Is anyone maintaining a database of these Dynojet run files? I think that would be a good thing to start doing. I have 3 files for my original motor, and 3 files from my Fish motor I would me more than willing to make public.[/quote]
I have lots of old runs of mine on a couple different motors, but I agree that it would be good to have data from a whole bunch of us. I coordinated with the dyno we had at RA in Jun? for the data. They didn’t use a F/A sniffer tho, so that made the data less useful to us. They told me I could get the data after the event. I must have tried to contact them 12x by email and phone in the months that followed. When they finally picked up the damned phone it was to say, “oh, sorry, we deleted that data last week.”

If a group of SE types have another Balanced Performance dyno day, I’ll put the issue on the skyline and maybe we can end up with data.

#16

It came with the car. I refreshed the top end at the end of last season.

I appreciate all the helpful hints–I’ll do spark / wires, and have my shop check the timing.

#17

Definitely inspect cam timing. Did you mill the head?

I would not throw any more money at it until the Cam timing was checked.

#18

interesting read. I’m tracking down issues with my setup and coolant temp might just be it. Dash works, but oem coolant gauge does not. If I read pin 45 and it does show that it is going into limp mode for coolant temp, is there an easy way to bypass that? or do I get new sensor, wiring, etc?

#19

I guess I should have followed up with this.

Compression was down a bunch. After staying steady for a few seasons, it just dropped off a cliff.

#20

Consider getting an aftermarket temp sensor and gauge. If you can, get one of the good ones with 2 wires to the sensor, a stepper motor, and ~270deg of sweep. I went thru a lot of happy-ass gauge solutions in order to find the most expensive and complicated way to do anything. I’d have saved myself a lot of time and money if I’d have bought high end gauges like STACK or it’s Autometer equiv with:
–2 wires to sensor so accuracy not impacted by ground quality
–Stepper motor and 270deg sweep for precise reading of temp with eyeball
–Data out to your data logger
–Programmable gauge color so the whole gauge face can go Yellow or Red at a temp of your choosing
–Programmable threshold out so you can run an external warning light.

Sometimes a person can go cheap and get away with it just fine. But other times going cheap means you slowly increment up buying and installing increasingly capable solutions until finally you end up with the solution you keep because it does everything you want really well. But then you have a pile of your discarded solutions that turned out to be a waste of time and $$.