Hey All,

I was having my car dyno tuned yesterday. It is a 383 HSR 6e w/36 lb/hr injectors.

However no matter how we altered the fueling we always hit a hard wall @4800 RPM.

I found a post thanks to TunedPerformance for extending the spark vs RPM table out to 6400.

My question, does anyone think this will help? My engine is rated max HP @5400 so I would like to be able to hit that.

Beyond timing we did increase the Max Maf Airflow vs RPM to allow more GPS 4k+.

We have also altered the PE table to get more fueling into these RPMS.

Per the logs, we never see more then 243 gps @4600-is before the the wall is reached around this point; so we should still have room in the maf tables.

Second question. Anyone have any other suggestions?

Thanks

 

There shouldn’t be a wall. What is it? Is rpm pull stopping? Going lean?

the maf will max out around 246-255, so thats normal. Timing wont do anythjng but is nice to control to 6400

There is a table called power enrichment vs rpm and couple of open loop tables you can try if fuel is a problem

pe enrichment vs rpm is what you need to add fuel and its usually 8-15% per 1 afr but can vary greatly lol

 

The wall we are reaching is that the RPM pull stopping. The RPM wall starts around 44-4600. At this time we are reading about 241-243 gps. The next sample at 4800-ish is 132 gps.

Whatever this "wall" as I call it we are hitting I can say we have added a bunch to the PE vs RPM table, shown below.



I plan to hit up the shop for the dyno logs. From what I remember seeing, we were ~12:1 up to 4600 where it started to hit the wall, and then it just stopped pulling around 4800.

The shop has all the pull logs from TP RT as well as the dyno logs, I will get them tomorrow so I can analyze them and see if I can update this with new information.

One other question I have too, are all MAFs created equal? For this build I bought this Spectra MAF and unlike the Bosch version I also have, this appears to be a new style MAF with a front to back mounted sensor wire vs the Bosch's side to side mounted sensor wire. Could my maf be causing this in any way?

 

Yeah so it acts sorta like a rev limiter? What does afr do at this point? Find that out

fwiw my 383 using aujl based bin i had to go to 70-80% pe adder to get afr in the high 12’s.

not sure on your maf but there could be a possibility its an issue. One place to check and rule out but if its working to 4600 not sure why it wouldnt work above it

make sure there are no obvious errors like ignition problems or rev limiters, fuel cutoffs etc

 

Yeah so it acts sorta like a rev limiter? <- exactly this. It just stops and falls flat. The AFR curve on the dyno graph also spikes hard(very immediate) upwards towards lean.

I will find the specific AFR tomorrow, but from what you are saying perhaps we just did add it enough fuel into the PE table.

Attaching two more images of the PE tables, one of the original values before our mod and one of the difference between current mod and original.





Will update further tomorrow morning when the dyno shop reopens.

Thanks!

 

Sure your intake tube is not collapsing at high rpm?

 

Not at all sure of that. It is the stock flex tube from my 87 IROCZ. That is a good thought, I wonder if it was. Good call, I will mention that too.

 

I ran the stock tpi intake snorkel and never seen it collapse but do check

for a test try adding a bunch of fuel value to those pe tables af 4800. Infact carry the values above 3200, the pe vs rpm enrichment should sorta look like your torque curve if you graph it. So try something big like 60% in the 4400-5200 range instead of 12-20. Not saying thats it but something to try to make sure its not a lean spike limiter effect

only other thing i have seen is if too much fuel it will kill the rpm rate, but yours doesnt look like it would add that much fuel there

the fact your 3200-4400 rpm range is alot higher than before and giving somewhat correct afr til 4600 makes me think you need alot more above 4000. Cuz if you have decent heads and cam, peak torque should be arriving between 4000-5000 rpm which is max air flow and thus max fuel

 

Hey all,

Got some data this morning. Looks like what may be causing it is a faulty maf sensor or so we are thinking.

Below is the TP RT monitor showing MAF Volts, TPS, RPM, and GPS for the last pull we did.



Finally here are two pictures of the last run as the Dyno saw it. The AFR is pretty steady until ~4600 when it tanks lean sharply.

 

not related here,
but some other point,s, that are often over looked,
especially if youve upgraded to a higher compression ratio,
350,383, or 400 based sbc engine in your third gen,
is that if you swap a significantly better flowing intake,
like the Holley stealth-ram,
on too what would other wise be basically a stock TPI engine the
stock O.E.M, exhaust is very restrictive
the STOCK CYLINDER HEADS are VERY flow restricted
The stock cam is limited to about 4700 rpm \
the stock valve train is far less than ideal
the stock injectors are not able too feed a significant boost in power
the stock HEI, *even a small cap aftermarket version, may need mods to work,
most O.E.M ignition wire is pathetic.
if youve upgraded the cam, you may require a higher stall speed converter

 

That does look suspect seeing that graph. Try a diff maf?

 

TPS voltage is pinned at WOT so that's good, but before it drops you have a massive down-spike in the MAF voltage and GPS that almost directly coincides with a HUGE lean spike in the AFR. I woulds say for sure something is desperately wrong with the MAF or at least the MAF signal as seen by the ECM. Either that or the engine just stops pumping air but that seems..... unlikely. Dropping from 200+ GPS to 70 GPS in the space of 1 second...... either you have a gigantic and intermittent exhaust blockage, you sucked a shop rag into the MAF inlet, or the MAF is dead.

GD

 

Orr89Irocz, GeneralDisorder, agreed. I ordered a new MAF today, it will be here tomorrow. I ordered the Granatelli TPI MAF as it is adjustable and of higher quality than what I can find elsewhere. I had considered the Delphi one, but was not confident that is would be better than my Spectra one, despite Delphi being a much higher quality than Spectra. With the Granatelli, I should be able to extend the range of GPS the ECM sees while staying within the 5v/255 max GPS available to the ECM, assuming of course this is necessary.

Does anyone have any experience with this MAF? I got clearance to return it if it does not perform as expected or solve my problem.

As to the engine I am running, it is this 383 from Blueprint using an HSR with the TPI throttle body. 36 lb/hr Holley Injectors.

 

Cant locate a good stock oem one from somewhere ?

I have not used any special mafs before

 

I tried looking for a stock style Bosch with no luck. The closest I could find was the Delphi one. I went with the adjustable one for a couple of reasons, one being the fact that my stock throttle body is 48mm which is already restricting the HSR which calls for 54 or 58mm(can't remember which). As it is, I am near maxing the ECMs GPS reading @4600 RPM(243 GPS), if I were ever to get a bigger throttle body, I might max it earlier. With the adjustable one I should be able to fudge the readings a bit without maxing out the ECMs GPS reading early.

 

I wouldnt worry about the maf maxing. Where ever it maxes you just need to tune the pe vs rpm to take over

 

Being it's a 91..... I have to ask - why aren't you just running it speed density with like an EBL P4? Obviously you are running a 7165 ECM at this point but yeah..... you could get an EBL Flash II to plug into the 7165 harness and go speed density that way. The EBL has extended VE tables all the way out to 8000 RPM. The EBL Flash II for TPI is like $475 plus shipping. Probably not much less than the Granatelli MAF and no limitations.

Just sayin......

GD

 

Thats a good question.

While the body is a 91, all of the wiring is from my 87, including the engine harness. Is it possible to convert the MAF 6e to a MAP using the EBL P4?

 

Not the P4 - You use the Flash II for that conversion. And yes it works GREAT. I have it in my 86 Trans Am that was originally $32 and then later $6E and now runs the EBL Flash II (which is MAP, yes. You can throw the whole MAF setup away - it uses a $15 GM MAP sensor instead). It's 10000x better than any stock ECM.

https://www.dynamicefi.com/EBL_Flash.php

Best of all - RBob the developer of the product is a frequent forum poster and helps the community with tuning questions, etc. His product support is unsurpassed in my opinion.

GD

 

That sounds wonderful. I'm sorry to ask but can you lay out exactly what I will need? I see a couple of add ons for the Flash II related to injector drivers.

Do I throw away the 165 ECM and plug and play this system?

Thanks, I am really thinking I will do this instead, just want to go in educated.

 

Also note a repin to 730 style harness is not all that terrible just need to pick up an extra ecm connector

but if ebl has a adapter harness thats much easier

 

It is basically plug and play - same connectors as the 7165 ECM. There are half a dozen or so wires that you must de-pin and either leave out or move on the connector. And then you must wire in the MAP sensor to the existing MAF wiring and I would highly recommend moving the MAT sensor into the air filter area as it now becomes the IAT sensor. Realistically, installation and basic setup takes about 1-2 hours. I converted my daily driver and didn't miss a day of driving it.

And yes you need the port mod option for $25, and it's best to just buy it with the ECM all pre-installed. You will need a windows laptop with a USB port for tuning.

GD

 

Thanks GeneralDisorder and Orr89Rocz!

I see DynamicEFI sells the additional connector I need to re-pin to a 730 ECM for like 5 bucks. Would it be beneficial to re-pin and use the P4 system? I am pretty good with wiring after this project. The only difference I can tell from his site between the Flash II and P4 system is 1 vs 2 fan control. I have a stand alone fan controller currently so that is a minor difference. Other than that, I would assume the standard SD differences remain, such as knock sensor, etc.

 

I don't believe there are any significant differences in features between the Flash II and the P4. You could contact Bob and ask him which way you should go but I believe it will be simpler to use the Flash II for you. They are both very similar on the programming side I do believe. The P4 has internal knock control, while the Flash II uses your existing external knock control module...... there may be advantages to the 730 style knock control but I would not know. I am starting a 91 Formula project though so when it comes time for needing a tuning solution the P4 will probably be my choice.

GD

 

Thanks again GeneralDisorder!

I went ahead and ordered the EBL Flash II today as well as a new MAP sensor and pigtail.

Cheers!

 

@GeneralDisorder
I just wanted to give you an update. I installed the EBL and well holy ****, I have a rock steady idle now. My MAF system would often fluctuate +/-1-200 RPMS.

This system is just way better then what I had. Been playing with spark timing and VE(13 learns so far) learns the last few days as my engine wants no more then 34 degrees total advance @3500 RPM, and it already feels more powerful.

Also adjusting the OL cAFR and PE cAFR to something that makes more sense for my vehicle.

I do get the stumble I saw you post about in your thread occasionally from a dead stop due to AE and am working on that as well.

Thanks for the suggestion and for anyone else having trouble like I did with the MAF system, I also recommend the EBL Flash 2.

Cheers!

 

Sweet! I've thoroughly enjoyed working with mine.

GD

 

Look forward to hearing updates on the numbers. I only messed with one ebl car and it was a blown 383 tpi car lol very torquey but the system worked well

 

Sounds good, I'll be sure to update once I get everything finalized!