Hi all!

Some weeks ago I have completed my Holley HP Conversion.
Before I had the stock 165 ECM with a custom tune I made together with a friend.

So far, it starts up very well, idle is pretty smooth and the driving feels good aswell - but somehow I think there could be alot more power, and the fuel mileage could be better
I currently get around 9-12MPG in mixed driving conditions.

Power figures are somewhere around 310-320 whp ( measured with my smartphone with PerfExpert, this was very accurate some years ago, not more than 5hp off a real dyno )

I think this is a little bit low for my engine, at least with the old ECM it produced around 330whp (which was still not enough in my opionion)


These are my "smartphone-dyno-results" :

https://network.perfexpert-app.com/results/nYYAUQ6enT


Here are some of the values my engine is currently running on:




Spark Table





Target AFR , as far as I know even WOT is controlled by the WB02 of my Holley system















Last but not least everything I know about my car&engine:

My old 350 block, bored 0.60 over , stroker Crank from Scat (think so) and Probe Industries Pistons etc.
AFR 195cc Heads (#1040) 65cc chamber , should be ~10.4:1 Compression Ratio

Jones Custom Grind Camshaft ( 280/286°; Lift .528/.535 109LC , at least thats what I remember )

Holley Stealth Ram Intake
Stock 2x48mm Throttle Body
Stock Intake Tubing, still using the old useless Maf Sensor within the tubing
SVO Redtop Injectors ( 30lb/hr @ 38psi ) , non-adjustable fpr @ 43.5psi

On the exhaust side:

Dyno Don 1 3/4" Headers , 3" Magnaflow Cat, 3" Magnaflow Catback





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Do you see something that could be a possible cause for having a bad mileage and a loss of power?

 

Are you running in batch or sequential? And this has nothing to do with your mileage but if you're not spinning up to 7000 you may want to change your tables for better resolution. Double check your timing as well to make sure it is what the computer thinks it is.
And your transient fueling tables look fat to me, that's a lot of accel enrichment in the first table. Although it'll correct, that's still having to pull out a bunch of fuel.
Jmo.

 

Hi, thanks for your reply.

I'm currently running at "Paired" injection. The other options are Bank to Bank and untimed sequential. Would it be advisable to use one of those?

All those tables are the base tables supplied by Holley, i just have edited the Spark Advance table a little bit. At the moment I don't know what the other tables do and where to start.


By changing the resolution of my tables you mean switching from a 16x16 table to 32x32?

 

Imo spark is alittle low around cruise areas. Sub 2500 rpm, 60-75 ish kpa range.
Also too rich there.

Map areas 1200-2500 in kpa of 56-77 i would shoot for 14.7:1 air fuel and 35-36 deg spark. Maybe even up to 84 kpa

That should be near a 400 whp combo.

Wot lean out abit more 12.8 ish air fuel. Afr head does better slightly leaner in my experience

I dont know what pair inj is. I would run bank or sequential

 

Thanks !
I'll give it a try. I think I will have some news by tommorrow.

I think "paired mode" is that all injectors fire at the same time.


Edit:

Did some changes ( at the moment all what Orr89RocZ suggested ) , that seams to help a little bit - but at WOT it seems that at ~4300-4400rpm the engine runs out of breath. RPMs rise but I don't feel any power increase from there on.

 

But even with these changes you MIGHT see a couple mpg change.
You need to find out exactly which injector mode you're in, how that works for your application, and what the duty cycle %'s are. That'll give you a point of reference to work from.


Hope this helps.

 

And a good bit of the mpg could be lost in AE transient fueling. It does seem to have alot of low tps opening fueling correction and tapers off with larger openings. Unless i am looking at it wrong

 

It'll correct for that though, it'll try to hit whatever air/fuel is entered in the corresponding area of the target table, unless of course it's past the limit of correction. But he didn't mention any drivability issues.

Imo there's most likely an issue of dumping fuel out the exhaust at some point. Again verify spark timing, injector timing and type of mode as well as injector %. That'll tell you where to go next.

Thanks.
Mark

 

Afr control is more of a constant parameter for a given condition

Theres no way it will react fast enough for pump shots. A quick throttle opening injection event can be over before the wideband ever sees the mixture

 

Yesterday, I did the changes you recommended.
It's running now at Untimed Sequential, with 36° spark beween 1200 and 2500rpm / 56 and 84kpa / and all the way through the wot cells.

I also changed the target AFR to 14.7 in those cells , and the WOT cells from 12.5 to 12.8

It seems that the engine likes that - I did a datalog while driving, unfortunately I left my notebook at work, so I just can tell what was going on within the log instead of uploading it.

While crusing the AFRs were around 14.3-14.9 , deceleration fuel cutoff worked aswell. Nothing special to tell - engine felt like it should feel I think. For any MPG related measurements, I will have to drive more.

At a WOT pull in 2nd gear (T56) , TPS at 100% , MAP rises to 105 , Spark Advance at 36° , AFR 12.5-13.0 , no Knock counts , nothing audible (but I am not sure if the knock sensor works properly...). In the upper rpm range (4000-6000) the MAP falls down to around 80kpa - does this seem correct?
Or could it be that this is a hint that my engine isn't getting enough air?

 

Bingo! Not enough air. Restriction at the intake filter and or throttle body

 

Hmmm.... at least now I know that there IS a problem and there may be some power hidden in the upper rpms
Hope I find a fast solution for testing, maybe a cone filter which mounts directly to the throttle body.

In the next days I'll do some further testing with the AE/TPS Correction settings.


Thanks alot guys, I'll keep you posted about the progress.

 

Yup filter to tb will be a quick test fix. But ideally you will want to get rid of the maf sensor and replace with the speed density version intake tube, and gut the filter boxes out of the tpi intake

Or better yet do a 3.5-4" air intake pipe to the headlight area.

Stock 48mm tb may still be a slight restriction

 

Here is the graph of the WOT pull - I was a little mistaken, the map didnt decrease down to ~80 , just 91-92 , but I think this is still a problem.

Just for clarification:
Purple : MAP
Yellow: AFR
Red: Injector Duty Cycle
Green: RPM

 

Yes, you still have a restriction somewhere.
And as far as correction on transient fueling, it'll depend on your O2 sample rate and processor speed as to how much enrichment "gets by" the correction. All in all it's still milliseconds. That's most likely not a significant cause for excessive fuel consumption.
However with a duty cycle of approx. 80+% you're probably about where expected on power.

 

Seems like its making some power. 91 kpa is still restriction as noted.

Work the air fuel curve some more to find max power on dyno. Play with timing. It may like alittle less in the peak trq area.

 

Today I had the time to do a quick testrun with maf and air filter removed, just the throttle body and the first rubber piece. Seems like it is breathing better than before.
I don't know how this is affects the reading, but it also was alot hotter outside today than last week. Today I had intake temperature of 150°F , last week only about 95-100°F.
It still seems to have a litte bit more power though.....

 

Is it sucking air from underhood?

Atleast map is remaining high. Thats a good sign

 

Yes i think thats because of the underhood temperatures.
Looks like I'm building a CAI in the next weeks....

Little update: On this sunny day I took my GTA for a longer distance drive and checked the fuel economy. With AFR's between 14.7-15.0 while cruising at speeds of ~ 70-90mph I managed to get around 20MPG, seems to be ok for me, what do you think?