I want to mazimize the tuning of my carb'd 2056. Short of seat-of-the pants tuning, I figure using a chassis dyno is the way to go. I haven't checked to see where the nearest one is or how much it will be, but after spending all this time and money building it, I'd hate to leave any power on the table. I'm just not sure how you go about using it to tune the engine.

I assume I should have the engine pretty well broken in and running well with the carbs jetted as good as my seat-of-the-pants dyno can tell.

Do I go there with a variety of idle and main jets, air correctors, venturis, etc and start swapping things out one at a time based on a baseline run?

I would spend as much time as you can using plug readings and maybe a dash dyno type device before using a dyno as it will be very expensive and not a quickly done thing.

Search for posts by Budman5201. He's out in Az and chassis dyno'd his suby powered 914. I don't believe he camped out there and tuned it. He could at least give you the going rate.

Before I'd do that I'd get a wideband EGA. You can dial your carb in just as good. You won't have a fancy printout with HP #'s though.

You can spend between $500-1000 tuning on a chassis dyno and it's quite effective. You need to either find a shop that is familiar with your carbs, or get proficient at working on them yourself. You'll likely need your own selection of jets to swap in and out. You're paying by the hour on the dyno, so once you're hooked up and locked down, you're paying for time. The faster you can make the jet changes and do the next power pull, the better.

Another tip is to find a dyno shop that has a machine that allows for variable loads. Lots of 'cheap' dynos are only set up for WOT power pulls. If you want to tune for full WOT, that's fine. But you may find that WOT tuning doesn't give you great around-town drivability tuning.

If you're looking for WOT tuning and will be doing some sort of racing, the dyno is worth it. If you're looking for great drivability and simply getting that as correct as possible, then you should invest in a variety of gauges (AFR, CHT, EGT) and simply spend a few weekends driving around and watching the numbers. You'll need to learn to interpret those numbers, but 'normal' driving can be difficult to simulate on a dyno, and therefore hard to tune.

Excuse my ignorance, but what is WOT power ?

No problem...
Wide Open Throttle.

To restate my comments above, a dyno is perfect if you're looking for the perfect tuning for a drag strip car, or an AX/DE/etc car, because those cars spend a significant amount of time at WOT. A street driven car spends almost no time at WOT.

Remember that everything is has some compromise. So a perfectly tuned WOT car very likely isn't tuned that well for 25% throttle.

wide open throttle power

Also tuning fi with a ecu is a lot quicker than carbs. You can drive and data log on a digital fuel injection ecu controlled motor. The dyno will only record that dynos hp and torqus numbers and it will vary between dynos. Also if the tires slip on the rollers it will be misleading.

I'm tuning solely for street driving, not track.

Any recommendations for a AFR gauge? Does this involve welding a bung somewhere on the HEs?

The dyno experience is only as good as the dyno operator.. Most chassis dyno operators are "tuners" that are accustomed to flashing ECUs, adding bling and looking for some magical HP gain.. Usually these gains are made at an RPM that is absolutely unusable on the street and are virtually worthless.

If you find a dyno operator that knows carburetors you'll be lucky..

I have a chassis dyno downstairs under my office... I love the chassis dyno because it affords the ability to test the entire car and all of its sub-systems at once and then lay AFR data over the TQ and HP plots..

Load that baby up and make a trip south, typically I can tune 15-25 HP into an initially tuned engine on the dyno in less than 4 hours and thats not 800-1K bucks worth of my time:-)

You are better off with a WBO2 and driving time than a chassis dyno experience with a less than knowledgeable operator.

the key is concentrating the tuning at the point where the engine will live the majority of its life.. big HP gains in the top end are virtually worthless for you.

yes, if you have a burch, the collector works well for the bung placement.
And innovative seems pretty popular.
http://www.diyautotune.com/catalog/wideban...stems-c-23.html

Yep you can make good power economy with a wide band.

You can actually see the carbs transition through the different circuits and tune for smoothest operation.

I used to own a Citroën 2 CV and I drove it almost always at WOT. With only 13 HP available, the throttle pedal is used as an ON/OFF switch

Mark and Jake bring good points. I have spent hundreds of hours chip tuning GM stuff and I found that when I get perfect results on the dyno it rarely works that good in daily driving. I now only use a laptop and data logger and tune and burn on the fly.

So, I would offer the same advice..... WB O2 and if there is some way to data log (even manually) I think you will be far better off tuning for real world driving. Sometimes the perfect reading just won't run right and you will notice that very quickly. In other words, sometimes the perfect "reading" is not the sweet spot

Keeping the stock HE's means you will be leaving significant power "on the table".
In addition to the variety of jets etc, you would need to bring other exhaust systems. You need to be prepared to change ignition timing to look for performance gains too. That means lots of dyno pulls with time between to allow the engine to ccol back down and to make your adjustments.

A much better way for you is to invest in good instrumentation and find a place to drive the car where you can experience a variety of rpm and load conditions including high speeds at WOT. You'll also need a good co-driver to keep an eye on gauges while you drive. Imo, instead of tuning for max power you should be looking for a balance between performance, fuel economy, and longevity (ie, keeping the engine cool).

i bought my innovate LM1 wide band O2 meter on craigslist for $100 with an LMA3 aux box. the owner wanted to buy the NEW color screen LM2. the LM1 plugs into the laptop so I didnt care about color on a screen.
now I wonder how I ever did it without a wide band.

I think Chris captured what I'm after (not max power at the expense of fuel economy and longevity). I do want to keep my heat as I drive the car from early spring until early winter, but I'm ok with sacrificing some performance for greater comfort.

I see that the LC-1 wideband O2 controller with sensor and guage is available for about $209 here.

Edit: I found one for $169 with the red digital gauge.

Are there target A/F ratios for these motors at idle, cruise, WOT? I assume different configuations have different target numbers.

Chris,

Call KTR Motorsports. They just finished up Greg Fulchers car.
They are more than capable of getting you want you want.

They have a chassis dyno and some of the best vintage mechanics on the east coast. Just take a look at the site and guess about the hundreds of cars they support.

Its not to far, Ayer is about an hour from you just off Rt 2.
No one will tune it better around here.
Rich

A nice header and 4->1 collector exhaust system will do as much or more for power gains from a Type IV than a small bump in displacement and tune. I know your weather is very cold, but consider a header and a wool ski cap to go fast and stay warm. Without a doubt, the used ceramic coated header was best $$$ I have spent on my 914 to date

At the last PCA meeting I saw an APP for a Draud???? You accelerate for a set distance and imput your weight (cars weight not your weight) and it calculates your HP

Anyone here more familier with this APP?

get the name of the app....look in the sandbox here a fre Droid apps were mentioned.
I have the phone, I will download it and try it tomorrow and report back.
My BMW is pretty well documented for stock HP and we can see how close the app really is.

Might be a cool thing to play around with.
Rich

Chris,

If you have an android phone or an Iphone you might want to give this a try. Repeatable results would be same stratch of road, same amount of fuel, same air temps, and same moisture in the air....but it will get you very close to see results....

I just downloaded the app and its pretty cool....might be a fun way to tune a car...I will give it a try with mine...

Rich

I spoke to one of the guys at this shop this morning for about 20 minutes. Seemed pretty familiar with 914s and IDF carbs. Nice guy. Gave me some tuning advice before ever bringing it to the dyno. The shop was started by J. Geils of the J. Geils Band.