SRT8 Dyno results less than you expected? LOOK HERE

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Mike_Levy
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SRT8 Dyno results less than you expected? LOOK HERE

Post by Mike_Levy »

Before posting up about minimal gains, or dynos showing power losses. Please, log your Knock retard. And when possible, get a Catch Can on the vehicle.

At this point in time, its common knowledge, that all Hemis, especially 6.1's have serious knock retard issues. You need to log your ST KR and adjust the tune to suit your car. All motors are different and all will require different adjustments, which is why the changes cannot be made in the canned tunes.

If the adjustments are made properly, you will not lose power. If you don't have the knowledge to make the changes yourself, find a CMR tuner who can make a custom tune for you.

The Catch Can is needed because the Hemi PCV system was designed by a retard, and without one, you're going to get a puddle of oil in the bottom of your intake manifold, which contributes to knock.



This thread may seem a bit harsh, but its reality. Deal withit. In fact, it should probably be made a Sticky. :twisted:
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NickLovin
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Post by NickLovin »

So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?

Just curious...

Thanks!
Raszaron
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Post by Raszaron »

I went to a tuner, who was recommended by some other dodge hemi locals, to get a custom tune and the numbers are what I ran. I am looking for some insight, not a ass chewing about putting up a post. As for a Newb, to some things, yes, such as tuning, that's what forums are for, to educate. If you get annoyed with that, then don't reply. As for common knowledge, maybe it's not, I am lucky if I get an hour a day to go on a forum to do research, the nature of my job.

PS. I use catch cans on my vehicles. And thanks for the advice on checking my knock retard (ST KR) values.
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mikel
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Post by mikel »

NickLovin wrote:So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?

Just curious...

Thanks!
We do desensitize the knock sensors in the tunes, but they have an oil consumption problem relating to the poorly designed PCV system (much like LS1/6's) which will always lead to KR no matter what, since oil dont like to burn.
Mike Litsch
DiabloSport Brand Manager
Diablo Tech support by phone:
561-908-0040
M-F 8:00 AM to 5:00 PM EST

tech@diablosport.com
NickLovin
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Post by NickLovin »

mikel wrote:
NickLovin wrote:So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?

Just curious...

Thanks!
We do desensitize the knock sensors in the tunes, but they have an oil consumption problem relating to the poorly designed PCV system (much like LS1/6's) which will always lead to KR no matter what, since oil dont like to burn.
Ohh, ok...

Yes, oil would much rather rapidly and violently combust at some random temperature and pressure than burn... :lol:
Quick
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Post by Quick »

NickLovin wrote:So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?
No, the factory tune is not to aggressive. And the knock is legitimate. and no, the threshold does not need to come down. Haha, all this is true because that's the way it was designed. People would like to think that the factory engineers or the SRT team are bumbling idiots and made huge oversights and errors but that's just silly. They designed to their criteria. One of those criterium is 100K (or something like that) duty cycle on the engine. Another is meeting emissions.

Take the catch can thing. They know about the oil. It's not like they missed that huge puddle in the manifold after the hundreds or thousands of stress tests runing the engine in various scenarios including to failure and then completely tearing it down. It's within the critera. Your engine burns most of it, some of it builds up and the engine runs just fine for at least 100K. Putting a catch can on the car to allow tuning for a little more performance is not feasible. There's the significant cost of the catch can, the cost of getting it EPA approved and approved in every single state, and it would have to have a huge resevoir to be sure to make it from one regular service interval to the next, yada, yada. And, no, I don't think it's due to a bad design on the PCV system. It's just that our motors inherently generate more atomized oil in the crankcase than others. LS motors do also.

Let's consider the knock (retard). The PCM is designed/programmed to handle that (up to a point). An event is detected and the PCM reacts to pull the appropriate amount of timing to eliminate it. It's variable. They have to design for widely ranging quality of gas, additives, and ambient conditions. From what I've seen the PCM does not over compensate. If you consistently get 3* of knock retard and you tune to eliminate it, you'll end up pulling 3* of timing. It's not like the PCM over reacts. (naturally you can usually adjust fuel to move towards the same end but that effects emissions, duty cycle on the cats, MPG, etc. etc.

With a tune (like with the Predator or CMR tunes) you can get another 20 to 40 HP? "for free". But you've just reduced a lot of margins. To realize that gain you're going to have to use good quality gas, you need a catch can, maybe a cooler t-stat, maybe tighter tolerance on air/fuel relative to timing, etc.

By the way, I think all the tunes desensitize the knock sensors to some extent. and false knock is VERY uncommon. I've only heard of it with aftermarket valve springs and maybe a couple of loosely mounted sensors.

But Mike's right. You do need to log to understand what's going on. Just looking at the symptom like a dyno result without knowing why is not very useful.
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mikel
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Post by mikel »

Quick wrote:
NickLovin wrote:So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?
No, the factory tune is not to aggressive. And the knock is legitimate. and no, the threshold does not need to come down. Haha, all this is true because that's the way it was designed. People would like to think that the factory engineers or the SRT team are bumbling idiots and made huge oversights and errors but that's just silly. They designed to their criteria. One of those criterium is 100K (or something like that) duty cycle on the engine. Another is meeting emissions.

Take the catch can thing. They know about the oil. It's not like they missed that huge puddle in the manifold after the hundreds or thousands of stress tests runing the engine in various scenarios including to failure and then completely tearing it down. It's within the critera. Your engine burns most of it, some of it builds up and the engine runs just fine for at least 100K. Putting a catch can on the car to allow tuning for a little more performance is not feasible. There's the significant cost of the catch can, the cost of getting it EPA approved and approved in every single state, and it would have to have a huge resevoir to be sure to make it from one regular service interval to the next, yada, yada. And, no, I don't think it's due to a bad design on the PCV system. It's just that our motors inherently generate more atomized oil in the crankcase than others. LS motors do also.

Let's consider the knock (retard). The PCM is designed/programmed to handle that (up to a point). An event is detected and the PCM reacts to pull the appropriate amount of timing to eliminate it. It's variable. They have to design for widely ranging quality of gas, additives, and ambient conditions. From what I've seen the PCM does not over compensate. If you consistently get 3* of knock retard and you tune to eliminate it, you'll end up pulling 3* of timing. It's not like the PCM over reacts. (naturally you can usually adjust fuel to move towards the same end but that effects emissions, duty cycle on the cats, MPG, etc. etc.

With a tune (like with the Predator or CMR tunes) you can get another 20 to 40 HP? "for free". But you've just reduced a lot of margins. To realize that gain you're going to have to use good quality gas, you need a catch can, maybe a cooler t-stat, maybe tighter tolerance on air/fuel relative to timing, etc.

By the way, I think all the tunes desensitize the knock sensors to some extent. and false knock is VERY uncommon. I've only heard of it with aftermarket valve springs and maybe a couple of loosely mounted sensors.

But Mike's right. You do need to log to understand what's going on. Just looking at the symptom like a dyno result without knowing why is not very useful.
OK, that stickys it....
Mike Litsch
DiabloSport Brand Manager
Diablo Tech support by phone:
561-908-0040
M-F 8:00 AM to 5:00 PM EST

tech@diablosport.com
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gsjoe
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Post by gsjoe »

Thanks for this educational post. It is much appreciated by me.
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Raszaron
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Post by Raszaron »

Great post Quick. Thank you.
Paladin06

Post by Paladin06 »

Thanks for the info.
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cleary524
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Retard!

Post by cleary524 »

Quick, Well posted! Thanks. Beans to you.
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jah81592
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RE: Retard!

Post by jah81592 »

I have tried to explain this to my customers (about the catch can) but sometimes they only hear what they want to. I agree with quick.-j
cavvet2
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RE: Retard!

Post by cavvet2 »

I used the datalogging to get rid of knock retard by adding fuel instead of retarding timing which would have the same effect of having ST KR - less power due to the pulled timing. Shortened life of the cats? Don't know or care... less mpg? I get 23 on the highway (2006 Charger SRT8) so I am happy with that. The fuel added only comes into play at WOT anyway and anyone measuring MPG at WOT conditions is gonna have sucky mileage anyway.

The results of months of datalogging and making adjustments a little at a time until the KR was gone? Well at the track running 104 fuel and adding 1 degree of timing advance to go with the better fuel I ran 12.8's with only my modded version of the 93 CAI tune, a catch can, and an AirRaid SRT8 CAI... Everything else was stock including the exhaust. I have since added a Corsa Catback and once again had to redo dalalogging and tuning adjustments... Haven't gone back to the track since then to see what improvements that made, but the whole point is you have to run datalogs and look at the results of them to know what changes to make to your tune. Make only one type of adjustment at a time and do it in fairly small increments then repeat the process until KR is gone (except for maybe a small touch at shift points) and the tune is right. Stock I was running 10.3-10.4 so I'd say the results speak for themselves.
The only question I would have for Diablo is why can't the canned tunes be done where they are at least a little bit closer to where they should be since everyone I talk to talks about how much KR they get out of the canned tunes. I know all cars are different but you'd figure at least some of them would run without a ton of KR out of the box as opposed to being close to where they should be.

I suppose I could pay a bunch of money and get my tune peaked even better than I can do it since the CMR software allows for adjustments I cannot make with my handheld but until I get more mods to make it worthwhile I am happy with what I have. WHen it runs the 12.8's now it feels like the blood drains from your face going down the track... I don't know how else to describe it... It is a great feeling however and when it happens to you you will understand exactly what I am referring to.

Good luck with your learning curve. I have learned a lot and still learn everytime I use my predator.
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crf450rr
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Re: RE: Retard!

Post by crf450rr »

jah81592 wrote:I have tried to explain this to my customers (about the catch can) but sometimes they only hear what they want to. I agree with quick.-j
A catch can is a must for these cars...
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crf450rr
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RE: Re: RE: Retard!

Post by crf450rr »

I know my car is not an SRT8 but,
Quick is so right about the gains you can get with a CMR tune...I have 3 bolt ons on my 07 Charger R/T
1. CAI (RDP with a Green filter)
2. 180 T-stat (Jet)
3. catch can (BT)
Stock with a K&N drop in air filter the car dyno'd 278 RWHP (I forgot the torque #'s)
With the 3 bolt ons and canned 91 CAI tune it dyno'd at 297 RWHP 344 RWTQ...
With the 3 bolt ons and a 91 CMR tune it dyno'd at 322RWHP 369 RWTQ...
The car will run low 13's all day on the stock GoodYears...
Very, very happy with the Predator...
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