Folks I have something a little different, a buddy and myself swapped in a a Honda d15 throttle body F.I. engine into his Joyner 250 sv buggy.
We used a VW transaxle for fitment reasons.
We have had the buggy running and after a bout a hundred miles or so of shakedown rides we are looking at drivabilaty refinements. we have a header on this with no cat, removed the top butterfly in the throttle bore and opened up the restricter plate.

Now it has a little more top end but it has some hiccups in the drivabilaty I would like to fatten up the fuel mixture a little and tune this for smoothest acceleration and have the broadest flattest torque /rpm range that can be tuned into this car due to the poor gear ratios in the VW transaxle.

Any info would be appreciated

 

You essentially took the worst engine and threw it in the worst conditions. There isn't much aftermarket support for the toilet bowl, ahem, I mean Dual Point Fuel Injection (DPFI). So using programs like TurboEdit or BRE are out of the question... If you want true ability to tune then you need to convert it to MPFI at minimum.

I see you don't understand the basics either... Anytime you run an open down-pipe like that you will lose torque. Plain and simple - to an extent you can gain horsepower but after a certain amount you will lose that as well. If you want it to run "richer" there are a few hacks you can do. There is the VAFC hack for ~$150-200 (You can just use an AFC as you don't have VTEC) or the old school tricks of resistors for the IAT and CTS... (Intake Air Temperature and Coolant Temperature Sensor).

To do it right and have the most support you will want to do your run of the mill DPFI to MPFI swap. Then an OBD-0 to OBD-1 swap, chip the ECU, and run a free tuning program like Crome. You could stick with the OBD-0 ECU, chip that, and use TurboEdit (preferably... it's all a matter of which GUI you like better (Graphical User Interface = Program).

Essentially with out a dyno and conversions being done - a "seat of the pants" or butt dyno it's the best way to tune any engine...

 

Thank You for the reply and the flame job
I hope I'm never that smart or important that I can't give a respectful answer but I'm just a redneck hillbilly so I guess I just don't understand.

ANYHOO....The engine was was selected because it was $300 for the whole running doner car. the Buggy my buddy already owned. but not enough power to go up any reasonable sized dunes. Were old guys here I'm 51 and my bud is 61. He is a semi retired machinest and I was an auto tech till I switched careers 7 years ago and now I'm a fabricator. I do realize that port fuel injection is better (even stock) and switching over to a programable ecu would be prerequisite to any advanced tuning. I also realize that a dyno is necessary IF I wanted the absolute best tune and every last available HP I could get, those are not our goals.

However I do have a wideband o2 air fuel gauge as well as the aforementioned butt dyno.
As stated in the original posting we are looking for improved drivabilaty . I was actually hoping someone could share some resistor placement and values, perhaps base timing or total advance info or maybe tweaking fuel pressure. I can't be the first guy to do these minor mods to this simple little engine and have some driveability issues.
This isn't my first rodeo..... I can figure it out on my own but thought I could save some time, trial and error by posting here.
maybe I was wrong ...... it happens

 

1.) You shouldn't take offense to people on the Internet, and this is a Technical Forum and these are basic questions.
2.) Age doesn't matter, I am in my early 60's myself. Over 40 years as a Millwright/Welder myself - it doesn't matter how big yours is either...

Now that we have the BS out of the way...

These are not old school cars where you can just dive and and start changing things around... You must understand that it is EFI - it looks for a set of parameters to operate in. Not only that but Timing is sealed with a lock and key inside the ECU along with total timing. Surely you could (going back to basics here) advance the distributor (which should be 16* BTDC standard) 2* or so at a time and run it until you get spark knock - then back it off a couple degrees to be safe. As far as adding/removing timing or fuel where you actually need it; you will HAVE to do one of the afore mentioned solutions...

The biggest problem you are facing is the technology. The DPFI is just complete garbage that doesn't respond well to modifications. It was made for fuel economy - the MPFI came in the vehicles that were "sportier". Rather than me go on and on about all this here is some good reading material for you. This will explain and show what you need to do...

http://qcwo.com/technicaldomain/iat-...-vs-real-chips

Regardless, you really need to get some better back-pressure on the exhaust otherwise your vehicle will suffer regardless. If you HAVE to keep the exhaust tight I would recommend an HF (D15B6) manifold with a resonator or two welded to an adapter for the manifold. This is a common manifold that kids use for budget turbo setups - they can be had cheap.

P.S. - I may come off as rude - but I am one of the few people on here that will go the extra mile to help you solve your problem. It just gets old repeating the same thing over and over when these vehicles have been around for 3 decades. People (mainly kids now days) are too lazy to do anything for themselves and pull up the Google and SEARCH.

P.S.S. - I just reread my first post and you are too sensitive... I went pretty easy on you.

 

1( I'm not so much sensitive, as I am intolerant of people that act like they know it all so everyone else must be an idiot.
2( My bad I mistook you for someone much younger.most mature folks are more polite.
3(yours probably is bigger........LOL . I only gave my background so we could get past the basic pat answers that most everyone already knows anyway.
4( I did search several different ways and found nothing useful, I suspect the reason is because it's not a favorable system and it's old school tech.
5( I FULLY understand this is fuel injected (duh) although I've never seen the lock let alone the key I do understand I can not change the timing curve. I do know I can change the base timing and therefore the total timing. I can figure this out on my own no sweat.I just thought someone may have some specific experience and some numbers to share.
6(I FULLY understand the difference between changing the fuel curve and altering the return voltage in order to manipulate the computer for favorable fuel ratio. remember this is not a street car we don't need 14.7:1 A?F ratio I believe we can run like mid 13:1's and overcome some of the hiccups and flat spots.
7( 2 times you have pointed at the header or exhaust as a problem stating it needs "back pressure" You should know the buggy is mid engine and only has about 4 ft of exhaust total. FYI it ran fine (for about 100 miles) till we broke a couple connecting rods(vented the fuel tank into the air filter system= dumb idea yeah I can be stupid at times LOL)
reassembling the engine I removed the upper butterfly in the throttle body and opened up the re stricter plate. Now we have some drivabilaty issues. Side Note: backpressure is a misnomer as you have explained it. It's more of a scavenging effect or air velocity of flow that causes the A/F changes that result in poor drivabilaty issues.
The exhaust is moot in this instance since we haven't had a problem till I opend up the intake. I will resort to putting the butterfly back in if necessary. There is no room in the buggy configuration to upgrade to port fuel injection. not only that if we get too much power then the VW transaxle may not be up to task.
If anyone else would like to know what I did and how things worked out speak up otherwise I'm going to consider myself on my own from here on.

Ps I understand this forum is your stomping grounds and I'm new here ,You can't know who your dealing with or what I may already know. But honestly you have not given me any useful info. You did succeed at amusing and annoying me though LOL

 

See now the full story is told... You never said anything about having not having problems prior to destroying the engine. If you truly were a mechanic you would know how important every minute detail is when diagnosing something with our being there. I grabbed a bag of popcorn and some laughs...

I can tell you haven't spent much time on a dyno... my exhaust comments are on point. Also - this isn't a built N/A engine... and the 14.7 is a target regardless if it's built or not for idle and 30% and below throttle - for drivability purposes. For what it's worth; aim for 12.9 -13.0 at peak TQ, lean it out afterwards to as much as 13.5 at peak HP, and play safe with 13.3's after that. Truth be told anything between 12.9-13.8 WOT can be considered acceptable as long as there isn't any spark knock.

Now that the full story is told - I would suspect something more along the lines of the timing is off - be it mechanical or ignition. I am at work so I don't have any timing maps I can pull out for you - but it shouldn't matter as you aren't tuning anything.

The MPFI swap will only get you maybe 10 BHP anyways - nothing that's going to break anything. The "upper butterfly" (tandem valve) and restrictor plate modifications should have nothing to do with drivability. As stated before - I would suspect timing issues or a sensor wasn't plugged back in properly. The ECU has a plastic window so you can see if there are any CEL codes being thrown.

Also, when you set the ignition timing again did you jumper the SCS pin-outs?

 

Bump.......