Hi guys,

I saw in a post here that someone would set his RPM to 2400 when he left his car at the dealer ship/garage.

Is this technically feasible? If so how, would the Tech II be able to do this change?

Thanks,



Cedric

 

This is a new one on me.

 

The rev limiter can be changed with tuning software, but I don't know about the Tech II. You would have to flash the computer before and after each visit.

 

Hi,

Do you know of any tunning software that wouldn't be to expense to acquire for this change?

Thanks,

Cedric

 

It isn't just flipping a hidden switch on/off whenever the mood strikes. It would require re-flashing or modding the parameters in the car's PCM computer. Each time. If there is another simpler way, I'm not aware of it.

If you are leaving the car for repairs, I would think that the mechanic would notice the low rev limit. If they investigate it and find out you've flashed the computer, your powertrain coverage is voided.

If, on the other hand, you are just leaving it in a parking attendant's care, it wouldn't matter... but flashing the computer every time you drop it off, and then re-flashing it when you pick it up seems more than a little nutty, not to mention a giant pain.

Cheers,
Kent

 

Hi Kent,

It's a bit more than that in fact and less often :o

My expat contract in the USA will come to an end on 9/15/2010 and I want to bring the vette back to France.

So that means a couple of things for me.

The first is autonomy, the Corvette is no longer sold in Europe, so I need to take care of the car myself. Which I have being doing for the past 2 years. No biggie for me.

The second is that I need to pass french inspections. One of the rough points that I still need to address at this point in time is the dynamic noise test.

The dynamic noise test, based on my understanding, is that the car is driven at 25 mph for at least 15 yards and the driver goes WOT for another 15.
The peak noise is measured during this test and it should not exceed 67 dB (from the top of my head). The Corvette gets a 72dB at this test which is a fail.
I am not sure about the 67 db but I know that I have get the car noise down by 5 dB.

Usually people constrict the exhaust with a butterfly but this means cutting up the exhaust and welding a butterfly to each exhaust. Which I am not to excited about.

Alternatively, my current thought, is to set the max RPM at 2400 (for example), so that when he floors it, the engine doesn't scream past the noise meter.

The dynamic noise test is done only once when the car enters the country and then finito.
Those who have preceeded me, unweld the butterflies and weld the exhaust back. Which sucks big time because you've ruined a perfect exhaust for some stupid test.

a++ Cedric

 

pack the exhaust tips into the muffler with steel wool, after a few weeks and launches it will burn out

 

5 db is a big difference. Every 3 db increase equates to a doubling of volume. You need to cut noise BIG TIME. If this is an in car measurement, dynamat and modeling clay are two items that can be used to cut in car noise. If it is outside noise, you can try what Dennis suggested. If that doesn't work, the rev limiting may be the only savior.

 

No kidding, 5dB looks like the Mount Kilimanjaro from here ... Measurement is done from the outside.

I will give the steel wool a try and see what it does.



a++ Cedric

 

believe it or not a friend of mine had a 69 camaro 396 with cam and side pipes it wouldn't pass inspection he went to a lawnmower repair store and found 2 round lawnmower mufflers that would fit in the side pipe end if he taped it in with a hammer, he started it and it just went real quiet like just an air sound forcing out the pipes, it passed, he stuck a dent puller in the ends and pulled them out around the corner from the inspection station

 

Interesting....

You could also weld/fabricate a slip flange resonator set up, bolt in and bolt out!

I personally think welding something in and cutting it of, is the way to go.

A local muffler shop would charge you $100-$300 bucks to do this...

THEN you buy a new exhaust system, with headers!!!

-Adam

Corvettes of Dallas

 

If you set the rev limiter to 2400 RPM and they go full throttle, they're going to know something is wrong when the engine starts bouncing off the rev limiter. Also, until you get to 2400 RPM, you're still going to get full volume from the exhaust. You may even find it'll make more noise when bouncing off the rev limiter defeating the purpose of the whole exercise.
Another angle you might try is to look at the other end...the intake side, more specifically the throttle. See if you can program the computer to limit the throttle to 25-50% when the gas pedal is floored. I tend to look at engines from the perspective of pressure ratios with wide open throttle creating the largest pressure ratio. Static compression ratios are simply volume related with air as the medium compressed and can be seen on the P-V diagram for the Otto cycle as the volume at BDC divided by the volume at TDC. The pressure ratio takes into account the "heat" added by the air/fuel mixture burning which can be seen as the highest pressure on the P-V diagram divided by absolute atomspheric pressure. Larger throttle openings add more "heat" causing higher pressures in the combustion chamber. Large pressure ratios have a lot of energy/HP and cause the loudest/deepest sounds when the exhaust valve opens to release unused energy. Without going too much deeper, limiting the throttle opening via the computer (even though the gas pedal is on the floor) will significantly attenuate the sound while still allowing the engine to rev past 2400 RPM and accelerate for their test. You'll get the added bonus of reducing intake noise to help pass the test. Return the program back to normal after the test and you're ready to RUMBLE!

 

There is nothing in the manual that states at what RPM the test must be done. It states drive at least 20 meters at 30 km/h before sound measuring device, then WOT for 20 meters. Noise to be noted is peak noise measured during this test. If the engine is limited to 2400 RPM this is a none issue because there is nothing about RPM in the test.

Putting it differently it is exactly like when I went to the NJ DMV to register my wife's car.

We bought a second car from an individual (friend of a friend) when we first arrived in the USA. At that time we only had our French drivers license.

I took the car to the DMV for registration under my wife's name, we got rejected at the dispatcher gate because we didn't have a NJ Driver License.

So I went again and asked a friend from work to come with me. He was sitting on the passenger seat and I was driving.

The dispatcher has a piece of paper and is checking off the lines on his paper. He comes to the point where he needs a NJ driver license, I ask my friend for his license and pass it on.
The dispatcher politely states: "Sorry sir, NJ Drivers license of the driver not of the passenger."

I look at my buddy and say let's swap. So we both get out and he sits at the steering wheel and then he hands over his NJ Drivers license (remember, car hasn't moved an inch in this process).

The dispatcher takes the driver license looks at it and checks off a line on his piece of paper and then states: "Please get out of the vehicle and go to the waiting room. I will drive the car from here on."

a++ Cedric

 

You're making this far too complicated.

Steel wool will make it as quiet as you want (although I can't imagine the stock exhaust getting my quieter).

 

add two dynomax bullet mufflers (on on each exh line) before the stock mufflers. That should help.

I'm from the "mother land" too...where in FRA are you from?
I've always been curious as to how the car import worked...in case I decided to go back some day...I'd like to bring our toys with us...sell them there and retire? lol surely a Z06 vette ought to bring some good Euros as well as my 69 BBC camaro...lol

 

I'm working for a company that is based in La Defense, Paris, France.

Regarding the return of any car in France it depends on the use, I'm going down the route a personal luggage which means that I will not sell the car when I get back to France.

The technical documentation and tests required are much less stringent when I go down that route. If you take the car to sell it, then it is a whole different because it is basically an import and the documentation required will be the same that GM had to produce.

a++ Cedric

 

i like the idea of reducing the throttle input. or maybe lower the ft'lbs in the torque managment tables to turn the car into a dog.

 

Once the car bounces off the rev limiter, they'll think something is wrong and fail the car.


I was thinking that you go in and pull timing accross the board to reduce power. Go into the IAT table and pull 10 or 12 degrees at all temps for all rows above mid MAP. Easy to reset when the car is done and there is no risk when driving the car home from the inspection.

 

Well GM did do something to Corvette that underwent certification and they certainly didn't put steel wool in the exhaust. Well I wouldn't think so

a++ Cedric

 

so basically you can never sell it? or is there a period during which you cannot, then after, you can? -just curious

My dad used to work at La Defense, for EDF...anyway, keep us posted how it goes, it isn't everyday that someone tries to do that and that's pretty interesting! definetly some good info! good luck!!