[grivera]

Assuming the same fuel is available, if an engine makes max horsepower with XX ignition timing, is it safe to run that same ignition timing setting in car/on street? How about chassis dyno ignition timing? Or is there a safety margin one should build in for street operation?

[Navy Horn 16]

If it is safe pulling a load in the dyno room, it's safe pulling a load on the street or chassis dyno. The engine doesn't know what it is hooked to.

[70GS455]

A dyno loads an engine harder than pushing the car down the street

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[Gary H]

But with a dyno you can typically keep the engine as cool as you want to make a dyno run. Not so on the street. If the engine runs warmer on the street it may see detonation that wouldn't occur on the dyno

[joes455]

Put my car on a dyno made best power at 38 and had detonation on the street,couldn't here it on the dyno.Only gained 8 hp from 36 to 38.There is a point of diminishing returns,at the expense of putting a rod out the pan.34 -35 would be safe with this combo

[joes455]

The same goes for af ratios going from 13 to 12 or vice versa shows hardly any gains or losses at wot

[JLMounce]

Road tuning is the way to go IMHO. It's a fairly easy process, it's just a little time consuming and most people don't want to spend the time to do it.

The engine dyno can't replicate the environment that the engine will actually be in. The chassis dyno (especially unloaded versions like the dynojet) can't replicate the load conditions the engine will see.

While both dyno's are important tuning tools and can help you dial in the engine for most power, road tuning will help dial in the car for where it's actually being used the most. On the street and only occasionally at WOT.

The simplest way to do this that will yield fairly decent results is to start by pulling back your ignition timing to a very conservative and known safe setting. For a stock headed, typical street build, starting in the 28-30 degree neighborhood is probably god.

With that out of the way, focus first on your fueling. Set your idle circuits by vacuum, the work towards lean while testing the car in normal driving and a repeatable WOT pull. Lowest gear possible to maintain safety, but where wheel spin isn't an issue. time the WOT run from a repeatable rpm to a repeatable rpm (2000-5000 for instance). Go in one direction in incremental steps until the car's readability becomes poor, or during the WOT run, it does not go faster, or slows down. Return to the previous incremental fuel change. Your fueling is now going to be fairly close.

Now work on the ignition timing (first without vacuum advance). Incrementally increase the total ignition timing until you either notice driveability issues or the car doesn't get's faster, gets slower or you hear ping. Back off 2 degrees.

Recheck your fueling to make sure the timing change didn't adversely effect fuel.

Then tune the vacuum advance at various threshholds and total additional added timing. Same rules apply start conservative and add until the car doesn't like it, then back off to the previous increment.

[grivera]

Thanks all. I ask cause on engine-dyno three years ago my engine made max HP with 38 degrees timing with a Holley 950 HP and headers. Up until this January I was using a Cliff QJet. Now my engine has a Sniper EFI controlling timing and I had my tuner set timing at 36. That being said, when it was on dyno the builder started pulls at 34 degrees. Since these are D-port e-heads with the fast burn chambers I now wonder if it would have made more power at 30-32 degrees. Max HP was 521. At 34 And 36 it was 510. Since my current choice for test and tune would be seat of pants would I be better off setting it at 34?

FWIW, Currently there is no audible detonation and engine is a beast.

[Formulajones]

The dyno told the tail. No need to second guess it. It made best power at 38. So if he started at 34 on the dyno and power kept climbing as timing was added, it's not going to make more power at 30 or 32.


Fast burn heads don't always mean less timing is better. Lots of variables and every engine is different.. My BBC for instance with AFR heads and heart shaped fast burn chambers made best power at 38 degrees, go figure. It runs that timing in the car no problem and has proven to run it's best times at the track with that timing. I've hit the timing retard button set for 4 degrees just for giggles and the car slows down considerably. .

Another odd one is dad's engine, with his old Edelbrock round port heads with the ancient bathtub chambers. Everyone says they need lots of timing. Not the case from what I've seen with these same heads on 2 different engines. First was a 455, and now on his 571, and both times on the dyno the engine made best power at 34 degrees. That's also where it's set and locked down in the car. No issues. And both of these cars push the pump gas realm with quite a bit of compression, there has been no need to dial back the timing.

You best bet now grivera, with no dyno available, is to hit the track and play with timing and look for best results. Otherwise it's a guess. But you already know where the engine worked best on the dyno so I wouldn't stray too far from that. If the engine is having detonation issues, it's probably a combination of many things. Not controlling engine heat, fueling, camshaft choice, quench distance, gearing, trans choice, weight of the car, elevation, and could be just as simple as slowing down the timing curve a bit.
If no audible detonation, have a close look at the plugs just to be safe. Black speckles on the porcelain.

[grivera]

Great suggestions- thank you

[joes455]

Detonation will show its face usually around off idle up to peak tq at wot .then timing can be added at the down slope from after peak tq to max rpm of combo.So u need to retard timing then add timing.

[joes455]

Our poncho needs a place for knock sensors.If u can hear it its way to late.

[grivera]

IIRC, the timing was locked out on the dyno cause at the time I had an MSD pro billet. Now my idle timing is 25 (ECU adds in 10 to simulate VA).

[Formulajones]

Originally Posted by grivera

IIRC, the timing was locked out on the dyno cause at the time I had an MSD pro billet. Now my idle timing is 25 (ECU adds in 10 to simulate VA).

That's not all that unusual to lock it out on the dyno, as they are mainly interested in finding best power with a total timing number.
So figuring out the best overall curve with initial, centrifugal, and vacuum on the street while keeping the best total found on the dyno is usually the end users job.
The default base timing for the Sniper is 15 degrees, and that sounds like what you are using. Adding 10 to simulate vacuum is okay, that's about all I will typically add.

Is this causing an issue?

[grivera]

Originally Posted by Formulajones

That's not all that unusual to lock it out on the dyno, as they are mainly interested in finding best power with a total timing number.
So figuring out the best overall curve with initial, centrifugal, and vacuum on the street while keeping the best total found on the dyno is usually the end users job.
The default base timing for the Sniper is 15 degrees, and that sounds like what you are using. Adding 10 to simulate vacuum is okay, that's about all I will typically add.

Is this causing an issue?

None at all- so far it’s running great

[Formulajones]

[mchell]

Not really answering your question directly but my experience playing around on the engine/wheel Dyno’s:

I’ve found the Pontiac tractor engine didn’t give a crap what the timing was between 30 and 35 total power wise...not enough to matter. What did matter was heat . More pulls made more heat and power dropped off. Makes it a bit tough to tell what the heck is going on unless you got all day to cool it down to the exact same temp every pull to ensure your change is netting you something.

Also, every time I set up to make most power on dyno’s, the car ran worse at the track. Lesson is that every situation calls for a different solution, dyno, street or track. Tune it for each rather than expect one tune to satisfy all conditions.

[mgarblik]

Originally Posted by Gary H

But with a dyno you can typically keep the engine as cool as you want to make a dyno run. Not so on the street. If the engine runs warmer on the street it may see detonation that wouldn't occur on the dyno

Our engine dyno is a Superflow 901 with a total loss water system. We can keep a 1000 HP engine at 120-125 degrees for infinite dyno pulls if we want. On pump gas, 150-160 degrees, makes best power in most cases. You certainly don't have that control on the street, in traffic on a hot day. Play it safe if you don't have a knock control system.

[HWYSTR455]

Another variable you don't have in a dyno room is elevation. You drive from the beach to the mountains, guess what?

Then of course there is fuel quality as you go from gas station to gas station.

I can't think of one instance that you can run the same timing, or carb tune, from a dyno to the street. If you can, or do, something is either wrong now, or when it was on the dyno.

Dyno time is valuable. Many engine builders don't have their' own dyno, and have to rent. Even if they do, they don't spend a day on one engine. So they pack up 3-4 engines and spend a day in the dyno. To find the 'best' 'dyno tune', you have to spend almost a solid day on the dyno, and most don't do that. They get a rough number and leave it at that. And, all they do is go for peak.

Shoot, lots of racers tune for the track and temp. If you drive your car year round, that approach doesn't work. And you will be accepting some type of compromise somewhere.

Just throwing some thought out there...

.

[Tom Vaught]

Originally Posted by joes455

Our poncho needs a place for knock sensors.If u can hear it its way to late.

My old company spent hundreds of hours $$$,$$$.00 testing on the Research Dynos to find the best compromise location for knock sensors.

The special blocks used had additional KSBs "Knock Sensor Bosses" cast into the blocks. Guess what: one side is different from the other side on a V-6 / V-8 / V-10 engine. So you need dual sensors (or go with the worse case side location).

So, Joe, if you can make it happen for us across the "high knock" power band on the Pontiac Engine and help identify those locations, my hat is off to you.

Tom V.