How much TIMING will a NA car handle?

[J DAWG]

Assuming one is tuning in the worst conditions. High heat, humidity and using 93 octane what is a safe range for timing. 30, 32, 34???

No knock sensors and loud exhaust makes it impossible to hear knock until it's to late.



So far 30 has been a safe range, but just wondering what some others have gone up to.



John

 

[jp]

The knocking most often occures where the tourque peaks. So how does your timing curve look?

 

[J DAWG]

most of my timing is from 4000 to 5000 rpms and then gradually falls off.

 

[Sean Roe]

With 93 octane, I'd say you're about right on target at 30-31 with stock spark plugs. You could go a step colder on the plug and possibly add a degree more.

To check for pinging while tuning, look at a few plugs with a high power magnifying glass, or jewelers glass. Pre ignition (hot plugs or low octane gas) and detonation (lighting the fuel too early) can show up as tiny silver or black beads on the plug. On a stock intake car, the forward cylinders run slightly leaner at full throttle, and the rears slightly richer.

Hope that helps.

Sean

 

[KenH]

I read somewhere that each point in octane = 2 degrees of timing. If that is true then from what Sean says it sounds like about 28 degrees is what I could do with the 92 Octane that we have around here.

What I find in practice is that if I add more than about 3-4 degrees at 4000RPM (25-26 total advance), then I start to get pinging. I'm running a fresh set of stock Champion plugs and using the sample NA fuel curve which if anything should put me on the rich side.

I have a WBO2 on order to get the A/F sorted out before I play with the timing advance any more, but wondering if there is anything else I should check that would affect the amount of timing I can run.

 

[FE 065]

I've seen more than one reference to using non-projected tips plugs to help reduce pinging or possibly detonation. Those same references state that all detonation occurs after the spark plug had fired btw and is the uncontrolled burning of fuel in the end gases.

 

[J DAWG]

Thanks guys. The discussion certainly helps.


Honestly, with my car I do not think I could hear detonation much less pinging until it is too late. Maybe I am wrong.


I have run a few runs with my a/f logged and I would get spikes at the higher rpm's and it was noticeable as the car ****** simutaneously as well while driving. I certainly hope it was not detonation.

Would detonation be more continuos or can it occur essentially in "one" area just one time(probably not a very good explanation of events). My car in inheriently runs rich, for now, so is it possible to get detonation when my A/F is low 11's or would it be something else?

 

[Doug Supercharged Vipers]

John -

You can have an acceptable a/f ratio and still have detonation.
And yes, detonation can occur at any given rpm at any time.

You should be tuning with a knock sensor and reading your spark plugs after each pull. We have a knock sensing unit that we use that emits a 0 - 5 volt output for data logging and displays a trouble light if spark knock occurs.

Properly installed knock sensors work well and you should be reading your spark plugs

Regards,
Doug

 

[Sean Roe]

....We have a knock sensing unit that we use that emits a 0 - 5 volt output for data logging....

Hi Doug,
The VEC2 has a 5 Volt output and 0-5 volt analog input we're not using at the moment. Sounds like you have something that would work well with it. I'll give you a call about it. I've been working on the logging software on and off for the last couple weeks, but should be focusing on it more soon, now that some other projects have wrapped up. We had planned to add a wideband input on the same circuit.

Regarding the timing, each car can be a little different. Most of my NA tuning testing was done on forged piston motors. Right off the bat, I'd have to suggest going more conservative on cast piston motors. Engine modifications play a critical role also, in regard to the timing curve.

Regards,
Sean

 

[KenH]

The VEC2 has a 5 Volt output and 0-5 volt analog input we're not using at the moment. Sounds like you have something that would work well with it. I'll give you a call about it. I've been working on the logging software on and off for the last couple weeks, but should be focusing on it more soon, now that some other projects have wrapped up. We had planned to add a wideband input on the same circuit.

Now your talking. I have a WBO2 with an unused 0-5V output and a VEC2 with an unused 0-5V input. Seems like just a little software and a wire connection away from having a closed loop WOT A/F controller in place. Add in Doug's knock sensor (are we out of inputs on the VEC2 yet?) and we've got automatic knock retard on the spark advance as well.

 

[Jack B]

J Dawg/Doug:

I have tuned four cars ((3)Gen2 and(1)Gen1) with the Vec2. I start by getting a flat 13:1 a/f ratio. Step two is to add timing, as soon as I add any timing above 3000, I get a V-notch in the power curve of 50-100 hp. This notch in the power occurs at approximately 4500-4800. It does not do it every time, but, it does not totally go away until the timing goes back to stock.

This is four different cars varying from stock to highly modified. The feeling is the same as JDawg is describing, it is a stutter as the rpm's climb. You can feel it on the road and feel/verify it on the dyno. The event causes the air fuel to temporarily go lean. The problem with this lean condition is that raw fuel hitting the O2 sensor will show lean, therefore, it is hard to diagnose if it is truly a lean condition. The car then recovers and the power continues to climb. It appears as a perfect V in the rising hp/torque curves.

I have talked to Sean numerous times and he is nothing but helpful, but, cannot explain the event. He has not seen this anomaly. In affect I cannot add timing where he has done so successfully. I have also brought the a/f down to 12:1 and the notch still occurs. Any suggestions would be welcomed.

 

[J DAWG]

Jack, sent you a pm. I have several things I would like to go over with you since you have tuned several NA cars.


John

 

[Go Fast For Life]

Jack B and J Dawg,

Please let me know what you learn about NA timing. I am thinking about changing mine too. I'd like to know if anyone else finds the V notch too?

Ron

 

[Torquemonster]

John -

You can have an acceptable a/f ratio and still have detonation.
And yes, detonation can occur at any given rpm at any time.

You should be tuning with a knock sensor and reading your spark plugs after each pull. We have a knock sensing unit that we use that emits a 0 - 5 volt output for data logging and displays a trouble light if spark knock occurs.

Properly installed knock sensors work well and you should be reading your spark plugs

Regards,
Doug

I agree. The old days when knock sensors were a pain in the neck because they'd trigger and detune so badly it made the cars slower than without them - is gone. With a good engine management system and properly setup - knock sensors are vastly better than guess work and good hearing.

Also detonation tends to appear in pockets rather than over a wide range if timing is sensible and the air fuel ratio is ok.... which is why most times you'd NEVER know. If the engine is knocking to your ear - it is severe, although it may be a simple misfire or intermitant failure to fire - which won't hurt the engine as bad but sounds terrible.

Some VEC2's have been dropping one cylinder or appearing as though they are at a certain rpm range. It has caused much head scratching because the same unit can work fine on another car. Several cars are affected by this both with and without boost. I know Jason Heffner and Sean have been trying to find a fix for this as while most cars are not affected it is very annoying for those that are.

There will be some happy people when the reason is discovered and a fix found. Jason tried something that seemed to fix one car that had the problem but it is too early to say it will fix all.... so hopefully the problem can be indentified and remedied soon. The VEC2 fills a valuable gap in the marketplace and it would be great to see them trouble free on all Vipers because they are so simple to use. They are a winner for the money for the majority that have no issues.

 

[Jack B]

Torquemonster:

As I stated before, this has happened on all four cars I have done. I had the same thought (a one cylinder misfire). The stutter always causes the a/f to rise during the anomaly. This is strange since you only have a 50% chance of affecting the a/f since you are only monitoring one bank. Perhaps it is something other than one cylinder misfiring. I do know the notch disappears when you go back to stock timing. What is also strange, I can move the 4800 rpm notch down to approx 4500 by removing timing at 3500.

I also believe the VEC2 is a major plus. I have the VEC2 bringing in my first stage of nitrous. I run that stage dry and also bring the fuel in with the VEC via the injectors. I get far more hp from the same jet versus the old method of a fuel solenoid. For some reason the hp hit comes in without the normal nitrous jolt, it is more like a transition. In my nitrous application I am not adding any timing, therefore, the notch doesn't appear. One more item, I tried removing timing (less than oem) when the nitrous comes in, there is a drastic drop in hp.

My dyno operator believes the timing advance is causing a hot spot in the cylinder or chamber. He also said what if the factory timing is optimized and cannot accept any more advance in the higher rpm region. What will be interesting to see is if the new AEM unit causes the same event.

 

[Viper Specialty]

J Dawg/Doug:

I have tuned four cars ((3)Gen2 and(1)Gen1) with the Vec2. I start by getting a flat 13:1 a/f ratio. Step two is to add timing, as soon as I add any timing above 3000, I get a V-notch in the power curve of 50-100 hp. This notch in the power occurs at approximately 4500-4800. It does not do it every time, but, it does not totally go away until the timing goes back to stock.

This is four different cars varying from stock to highly modified. The feeling is the same as JDawg is describing, it is a stutter as the rpm's climb. You can feel it on the road and feel/verify it on the dyno. The event causes the air fuel to temporarily go lean. The problem with this lean condition is that raw fuel hitting the O2 sensor will show lean, therefore, it is hard to diagnose if it is truly a lean condition. The car then recovers and the power continues to climb. It appears as a perfect V in the rising hp/torque curves.

I have talked to Sean numerous times and he is nothing but helpful, but, cannot explain the event. He has not seen this anomaly. In affect I cannot add timing where he has done so successfully. I have also brought the a/f down to 12:1 and the notch still occurs. Any suggestions would be welcomed.

JACK-

I have tuned 3 cars on the dyno here, a 2001 ACR, a 2001 RT/10, and a 2002 GTS. All of them had the exact same occurance that you speak of when advancing the timing beyond stock- however, I have found that it shows on the graph only after doing at least 2 pulls... generally shows on the third pull, unless a long cooldown is allowed. Once I grab a VEC-2, it will be interesting to see if the gen-3 is plagued by the same...

 

[KenH]

I would have to say that my experience at the track is similar to what is mentioned above on the dyno.

The car appeared to be running fine on the road during some full throttle 4th gear pulls. No stumble, no noticeable detonation and I was only running a couple of degrees of advance and probably overly rich on fuel.

At the drags, on the 1st run the car stumbled noticeably at around 4500 RPM for a short time, then pulled hard again. On the 2nd run, the car stumbled even worse at the whole top end starting around 4000RPM or so. On the 3rd run, I backed the timing down a bit and it seemed to run even worse and stumbled shortly after launch. Frustrated, I then backed the settings back down to stock and the car ran fine. To me, it felt like the car was missing on more than one cylinder and the power really fell flat. The next day everything seemed to be running fine again even with the same advance dialed back in. Had me scratching my head. At the time I assumed that I may have had a loose connection or something, but sounds like others have experienced something similar.

The stock advance has a significant dip around the 4000-4500 RPM range and it makes you think that the Dodge engineers knew something or they wouldn't have put it in. That is around the torque peak, so there may be a correlation there.

I got a WBO yesterday and hope to get it installed this weekend and dial in the A/F, then start playing with the timing again on a dyno.

 

[Jack B]

What would be interesting to see is an O2 sensor on both sides to see if the condition affects both banks. The "V Notch" (hp drop)low point coincides with the peak of a small increase in a/f. The the two V's (one up and one down, line up perfectly). The event drives the a/f change, not the reverse or norm. It is still hard to dianose since raw fuel will make the O2 sensor read lean, therefore, you don't know if it is truly a lean condition or the engine dumping unburned fuel.

I have the O2 sensor in the collector, therefore, my power and a/f curves are synchronized. If you put the O2 sensor in the tailpipe the a/f doesn't exactly correlate with the power curve it will be off by 500-700 rpm's on the dyno chart. It is still accurate, but, the curves are offset.

If I had not seen JDawg's post I probably would not have responded. I was starting to think that this problem was unique to the cars I had done. Sean is so above board, it is a wonder he hasn't seen the problem himself.

 

[Sean Roe]

Hi Guys,
Regarding the occasional, and only on some cars (but not ones with our blower kits ?) hiccup / stumble, it's not something we're dismissing or brushing under the table. It's extremely odd.
Jason Heffner was one of the first tuners to use the VEC2 for an application other than our blower. They've purchased many, yet some cars exhibit this phenomena while others do not. For example, he was tuning a customer car that had one of our our blower kits on it and the car was running fine. So, he decided to take that VEC2 and harness off the customer car and put it on a car he had there with SC or turbo that was experiencing the hiccup / stumble. The problem stayed with the car, even though the VEC2 was changed from the other car. When swapped back, the car with our blower ran fine still. We've tested a few for him here as well and have never been able to get this phenomena to occur. We've heard about it a little more (as read above) since we've sent out about 75-80 VEC2's as stand alone units, but to date, there still doesn't seem to be a correlation on what it is. We've done logging as well.
This reminds me of what we went through when developing the first Supercharger kits. We'd have something going on that would finally show itself through the same thing happening to a number of cars. That's how we found out about the stock injector connectors causing problems (which is why include new ones with the Supercharger kits) and the ground problem with the cars. In time, we will see what is going on here as well. If it's something we can fix with the VEC2, we will update the system and take care of it. If it's something to do with the cars, we'll make the suggestion to make a modification (to the car or the program) in the VEC2 manual / troubleshooting guide. Meanwhile, we'll keep listening and looking into it.

Regards,
Sean

 

[FE 065]

Can you do a plug chop and examine the plugs to see if it's truly lean at 4500-4800rpm?


Next time you get a car acting up run it at that rpm range for awhile than kill the motor at that rpm, and pull some plugs, - or all the plugs and see how things look.

 

[txlen]

man!!..you guys are going thru the same thing i went thru with the VEC2 n/a car i did!!!..i had a stumble around 4200 then again around 4700..after first doing the dyno route and setting up a safe tune it stumbled on the street in 3rd gear at those rpm's..and i could duplicate it almost every time on the street..i got my adaptives real close on both sides and the drivability cleared up alot!!...but the stumble was still there......i took some timing out if the car in both areas and it has cleared it up...and it's been stumble-free for 2 weeks now....Len

 

[HOdbleFman]

I'm getting ready to put my car back together this weekend after heads/cam. All this talk has me worried. You guys get this figured out so "slow" people like myself won't have to deal with it.

 

[Sean Roe]

It could literally be "just" more advance than the engine can take. We really need to get a car in the shop that does it so we can try different adjustments ourselves.
Our shop GTS with blower and 9.1:1 compression (bigger combustion chamber volume) is running 5.5 degrees advance (over stock) in the 4,000-5,000 range and always pulls smooth to 5,700 (where I shift when running it hard). I can e-mail the cbc file to anyone who wants to see it.
There's got to be some correlation that I'm not seeing yet as the cars with our blowers aren't doing anything odd and neither are the majority of the other cars. But some are experiencing this. The only things coming to mind are: grounds, injector connectors or excessive timing advance for the condition (?). On the blower kits, we supply an additional ground wire, new injector connectors and I do (most) all the Smart Card programming here.

Regards,
Sean

 

[FE 065]

That it could...It's a big bore, and end gases could be igniting off to one side or another under the right conditions.



It'd be interesting to see how an engine coated on the pistons and combustion chambers with a thermal barrier to keep heat in the conbustion chamber instead of the piston or cylinder head, and spread the heat more evenly on the surfaces might have its' detonation characteristics change.

 

[Torquemonster]

Good post Sean - would you mind copying it over to the other thread as well - because it might help someone who does not visit this one. IT'd look better coming from you than me copying it.

 

[J DAWG]

It could literally be "just" more advance than the engine can take. We really need to get a car in the shop that does it so we can try different adjustments ourselves.
Our shop GTS with blower and 9.1:1 compression (bigger combustion chamber volume) is running 5.5 degrees advance (over stock) in the 4,000-5,000 range and always pulls smooth to 5,700 (where I shift when running it hard). I can e-mail the cbc file to anyone who wants to see it.
There's got to be some correlation that I'm not seeing yet as the cars with our blowers aren't doing anything odd and neither are the majority of the other cars. But some are experiencing this. The only things coming to mind are: grounds, injector connectors or excessive timing advance for the condition (?). On the blower kits, we supply an additional ground wire, new injector connectors and I do (most) all the Smart Card programming here.

Regards,
Sean

Seam, I ordered the connectors yesterday and will put those on when they get here. We have spoke about bringing my car over to let you look at it and honestly if it continues after a few more changes I have planned then I will certainly haul it over to you.

I will be looking at my fuel setup closely and try to rule it out, but in your opinion is a "stock" viper fuel system capable of handling 540-550 rwhp. I am just trying to figure out if the injectors are maxing out or if I need a better pump and if the VEC2 is magnifying the problem that may be totally unrelated to the VEC2.


Thanks for all your help
John

 

[GTS Bruce]

Write when you out program the DC viper engineers.Write when you can justify burning a NA motor for 20 HP.NO VIPER NEEDS MORE HP.Better driver,better brakes and tuned handling is where some improvements can be made.NO one passes a Viper under power on a straight.Its brakes,handling and technique that can stand an improvement. Bruce

 

[RedGTS]

Write when you out program the DC viper engineers.Write when you can justify burning a NA motor for 20 HP.NO VIPER NEEDS MORE HP.Better driver,better brakes and tuned handling is where some improvements can be made.NO one passes a Viper under power on a straight.Its brakes,handling and technique that can stand an improvement. Bruce

Well I guess that's it then. Someone call Roe, Heffner, Levin, Macedo, Cragin, etc. and tell them the party's over. Last one to sell off their remaining inventory turn out the lights.

 

[Jack B]

Bruce:

Dragstrip is spelled dragstrip. If you ever experienced 700-800 hp you would have different thoughts and yes some of us also track the car.

 

[Torquemonster]

Write when you out program the DC viper engineers.Write when you can justify burning a NA motor for 20 HP.NO VIPER NEEDS MORE HP.Better driver,better brakes and tuned handling is where some improvements can be made.NO one passes a Viper under power on a straight.Its brakes,handling and technique that can stand an improvement. Bruce

Bruce - you need to get out more.

A simple cam and head package with exhaust and air upgrade is good for adding well over 100hp at the wheels - and that is enough to pass your stock one given they get the same exit speed into the straight.

Throw in a blueprinted and balanced race shortblock with some oiling upgrades and even you will notice the difference.