who does this mod?

[Marv S]

Are any tuners modifying the engine computer? (other than the piggy-back items)

If the engine computer is “re-calibrated” does it need a CARB test/number to comply with 50 state smog certification?

I keep reading about this Viper electronic tuning on the VCA FAQ page and car magazines but is it real?:
http://www.viperclub.org/faq/techfaq.html#fuel

“Chrysler engineers have said that over 500 hp is available from the current engine with only electronic changes. The side benefit of this reprogramming of the computer is better performance without driveability compromises.”

and How high of a CR can the heads be decked to and run fine on pump gas in the sumnmer?

 

[Anthony - 98 GTS]

Mopar used to sell an aftermarket "Performance Computer." The results where mixed at best. Stock cars usually saw zero gains and some hightly modified Vipers picked-up some HP.

Overall it was a bust and the unit is no longer sold. I don't know of any tuners currently modifying the stock computer programs.

 

[JimDavis MT 97GTS 650R]

Hi Marv S. I know tuners were able to reset certain limited functions of the PCM like idle speed in the past. The MoPar "performance" PCM is NOT available anymore as far as I know. Your best bet would be to go the VEC route from Roe Racing I.M.O.

 

[HouseofSpeed]

Stock ECUs can be piggybacked and reflashed....its all in who you know.

 

[Bugeater]

HOS,

Are there reflashes available to pick up the lost midrange due to the sh1tty timing maps etc..?

I have a Mopar ECU, and wouldnt mind getting that reflashed with a map that actually picked up power. I would LOVE to see someone try and get 500 ponies (assuming they meant 500 to the wheels) out of a stock motor with a new brain.

 

[Marv S]

Kyle, Still got the lightning? You know someone who can reflash and get the results the Viper Engineers stated from that action alone?

Thanks, Jim. I remember hearing that Dan C had reflashed to bump idle speed several years ago. Haven't heard many good reports on the MPP ECU and the qualifying line in the catalog was something like "50 hp if used with performance headers, GTS-r rockers, smooth tubes, & K&N. filters, (maybe even tb's)". Those mods alone were good for the 50 hp.

But where is a flash or unit that gets the 50 hp from only a recalibration?

 

[SapphireGTS]

Stock ECUs can be piggybacked and reflashed....its all in who you know.

I was at a track in Detroit. There was a strangely familliar guy there. He had a gts that he trailered there. I started talking to him and looking around his car. Then it hit me. This guy was in viper magazine last year. He drew up the VIPER concepts. He talked about a MOPAR computer that he got from the guys from R&D. Supposedly picked up 40-50 HP.

BTW - I forget his name but he was a really nice guy and was excited to show me what he had done to his GTS. Mods included swamp buggy rear mufflers.

 

[HouseofSpeed]

It is possible to pick up the areas that really **** in the stock program...and the spark map is a big player there.

Give me a shout and I will fill you in....281-821-3559, or e-mail / PM. Thanks.

P.S. 50 rear wheel is a tad optimistic.....more like 50 flywheel.

 

[Torquemonster]

and How high of a CR can the heads be decked to and run fine on pump gas in the sumnmer?

Shaving heads and decking blocks to gain compression is a cheap way to buy more cylinder pressure and all the detonation a hot day and bad gas will bring with it.

I wouldn't go that route, I'd be thinking more in terms of tightening the quench clearance - you'll gain more and have increased resistance to detonation.

there is only one tuner I have communicated with that is up on this - PM me and I'll give you some specifics if interested. This is one of those "tricks" that have come hard won by race engine builders so giving it all away for free in a forum punishes those that use things like this as an edge. Therefore I'd rather support them by referring you than going public. Lets support those in the Viper community that are innovating rather than tell all.

 

[Fast Freddy]

assuming you still want to run the 91 octane gas that is sold here in arizona, i would not go more than 10:1 on the compression ratio. a ls6 engine in a vette is 10.5:1 and gets away with it because 8 cylinders creates less heat than 10. i will be milling my heads to get 10:1 comp. ratio on my viper when i have them cnc ported and the bigger valves installed. don't forget u have to mill your manifold 2. i will still use my stock cam in order to pass emissions. i have a set of 1.7 ratio t&d roller rockers that i will be installing to give me more lift on the cam and free up some friction. lift and duration both give u more power, but increased duration and tighter lobe seperation angles make it harder to pass emissions and make for rougher idling.

 

[opnwide]

There's nothing special about optimizing quench (squish) area. Shoot, I've known this for 10 years, and I'm a 33 year old dentist. If my engine builder doesn't know about the quench area, then I'm taking my stuff somewhere else. Check out any of David Vizard's books on performance cams or performance heads at the bookstore. They're mostly copyrighted around 1990. Good, solid info. He specializes in chevy, but I'd bet he could grind one hell of a Viper head if given a few chances!


The modern chevy v-8 has run up to 11:1 compression because of optimization of this quench zone (and also due to reverse cooling), and these were "conservative" factory fuel/spark maps. 10 or 10.5:1 compression with 92-93octane shouldn't be a problem with a proper fuel/spark map worked out on a dynojet.

The new AEM engine controller sounds very promising, and it should UNLEASH the power of the Viper. I'm very excited about it. Yeah, probably worth 40-50hp in stock tune! It is designed to plug in (ie replace) the factory computer. Very stealthy. It'll have spark retard capabilities as well, I understand. That is something that is sorely missing from the factory computer.

 

[opnwide]

Also, 1.7 rockers will increase lift and increase valve overlap, the real culprit of a rough idle. The LS1 cams are ground with fairly long durations, but GM increased the lope separation to decrease overlap so that they could still pass emissions.

By the way, just a bump in compression increases emissions. However, not all states check for all gasses of vehicle emissions, so you may still be ok, here.

FYI. Personally, I believe that most vipers are kept in such a nice state of tune that a moderate increase would still be acceptable under most state standards. I've even heard of catless cars passing a sniffer test! Go figure.

 

[Dyno Dave]

That guy in Detroit was using the P5007721 Mopar PCM. It was released into the parts system last year but I don't know if they are actually available.

I don't believe that you can extract 500hp from a "stock" engine unless it's the SRT-10 and it does it out-of-the-box. Some hardware will need to be changed. There aren't any corporate policies or anyone keeping any "extra" in their backpockets in the calibration portion of the engine development.

 

[RedGTS]

FYI, I think the performance PCM Sean Roe sells (and which I have on my car) is the Mopar PCM. How he gets them and no one else seems to have them I don't know.

 

[Vipermed 97.01]

FYI, I think the performance PCM Sean Roe sells (and which I have on my car) is the Mopar PCM. How he gets them and no one else seems to have them I don't know.

The Mopar perfomance PCM has been discontinued amd definetely not recomended in S.C cars as there is to much timming advance.The one Sean carrys is for the 00 and up which is 97 ect pcm that takes better to mods such as S.C

 

[Torquemonster]

opnwide - you are of course very correct re quench being well published by David Vizard - the problem is that the actual specific specifications and how to optimize it on a specific engine combo is an art not one in 10 successful tuner/engine rebuilders use - and with Chryslers the ratio is even worse.

The cost vs benefit is not there for the majority of customers because they'll get more bang for buck by just adding headers and ported heads.

Like blueprinting - it is painstaking. Typical published clearances recommended are not actually the best - they are "butt covering clearances"... that was a tip.

I'll see if a special announcement in this area can be made soon... in meantime I'll leave it there It's a bit of a catch 22 - if we talk - everyone knows including competitors, if we don't it is a competitive edge but useless for marketing because no one knows.... dang

 

[GTS Dean]

assuming you still want to run the 91 octane gas that is sold here in arizona, i would not go more than 10:1 on the compression ratio. a ls6 engine in a vette is 10.5:1 and gets away with it because 8 cylinders creates less heat than 10.

Heat is a function of the engergy of fuel/air mixture being combusted. Except for friction, it has nothing to do with the number of cylinders. The Chevy engine has either a better combustion chamber design, or they have worked the ECU map over pretty hard.

 

[opnwide]

TorqueMonster,
It seems you know what you're talking about. Dean is also pretty sharp. Glad to have you guys posting on the board.
Greg