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996 Turbo / GT2 Turbo discussion on previous model 2000-2005 Porsche 911 Twin Turbo and 911 GT2.
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Modified OEM Muffler 996TT

 
  #31  
Old 06-30-2007, 12:34 AM
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My Remus sounds better and has dyno numbers to back it up. I have never seen a Turbo exhaust with no drone at 2-3K rpm... even stock has some drone
 
  #32  
Old 06-30-2007, 11:57 AM
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Remus, et all, may be wonderful but this is about what the stock exhausts systems are all about and what can be done with them. I have modded Porsches since the late 60s and the aftermarket will always jump the Factory where there is an opportunity for gain and to make money. I think most of us know the Factory also leaves some on the table for things like, GT2 and X50 upgrades without tearing into the internals. BUT this particular subject is about modding the stock stuff, ok? PLEASE, if you want to tell us how good a Remus is, I do want to hear about it, but please post a separate thread and give us SPECIFIC details about the car and what it already does or doesn't have or all you will end up with with is another "mine is better/bigger than yours" discussion. I AM curious about the aftermarket stuff also but there is a serious lack of genuine facts about what they do or don't do. In the past when I have seen no data, I usually figure there is not published info because whomever is selling this stuff is promising results they cannot back up. So, please... give us genuine info and on a separate link. Meanwhile, I would love it if we kept this about the Factroy stuff and what does or doesn't work. I am sure a good aftermarket system SHOULD be better as someone building would have a specific goal and a large potential profit margin to play with. I hear that European Cars is going to publish a comparison of some of the aftermarket systems in the next issue. I am sure some systems will get left out but it may give us a clue.. HOWEVER, I doubt they will give us comparison of stock 996tt vs GT2/X50 and certainly not a modded stock system. SO we gotta do it here or it ain't gonna happen!
JR
 
  #33  
Old 06-30-2007, 11:17 PM
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In the youtube vid it has a nice growl but seems pretty freaking loud. Is it?
 
  #34  
Old 07-01-2007, 12:16 AM
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Originally Posted by roadsterdoc
In the youtube vid it has a nice growl but seems pretty freaking loud. Is it?
Chris
I love your exhaust!!
Robert
 
  #35  
Old 07-01-2007, 08:08 AM
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We are dying to hear "he he,,,,,that was bad" the news.


Let us know!


(I have an appointment with my mechanic on Tuesday to do the mod, so I really need to find out if it loses a lot of HP ......I am pretty sure it won't).


THANKS!


(And this is not supposed to be mine is bigger than yours....as noted by others. )


JB



Originally Posted by wooosh
Sorry for the wait on results, I was tied up with family business this last weekend and had limited time. I was originally going to drill the mod holes in the exhaust during the little time I had allocated on the weekend then dyno this week, but decided for consistency in reading output on the dyno that I wanted to have the car strapped down and do the mod after I dynoed a few runs on the same day, with the car strapped, then multiple runs back to back.

Just knowing the Dynojet there are small variances from strapping, SAE correction, fan placement, cool down time, etc that I am going to do my best to minimize, especially since we are most likely dealing with a few HP, and not something that is so obvious.

I am looking forward to testing it, and I am trying to make time to do it properly, I will post all conditions results and pics...
Vince
 

Last edited by jcb-memphis; 07-01-2007 at 08:50 PM.
  #36  
Old 07-01-2007, 08:11 AM
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Sounds like an exhaust leak
 
  #37  
Old 07-03-2007, 09:27 AM
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Hey, I did go to the Shop Sunday night and dynoed to get a baseline witht the UMW chip and Stock exhaust. I purchased the drill bits and extensions I needed for the holes.

Since we are talking about a potentially minor change in HP from the exhaust mod I want to make sure I have clean repeatable numbers, which I did NOT get the other night. As I mentioned before my baseline before the UMW was repeatable at 388Hp and 401TQ. My first couple of runs after the UMW chip were all over the place 425-438HP and only 419-450TQ, which both should be higher, especially the TQ. The car is pulling back timing, it was hot I had two cage fans one on each intercooler, and one on the front, and static air for the intake. The car is not slipping nor is the clutch.

Some people pull the bumper cover to get decent cooling of the intercoolers which I did NOT do. I did NOT spray them with water/alcohol mist before etc. With the higher boost levels of 1.0-1.1 cooling is more of a factor and it was fairly hot in the shop. I did NOT drill the holes yet since I have not gotten a repeatable number first.

On the street there is significantly more air flow to the engine and intercoolers. I have no sensation of timing being retarded on the street, it pulls strong.

I am going back to the shop tonight and I am going to put a fan on the intake, wait until about 10pm tonight when it cools down ambient temp. mist the intercoolers and ADD RACE GAS to make sure there is no timing retard. Not sure if I will pull the bumper cover or not. Race gas will not make more power than my 93 local octane unless the timing is being retarded. My tune from UMW is 93 octane, I also need to research locally if there is any methonol added to our gas. Usually stations post if they do enhance with Metanol.

If I get repeatable numbers then I will try the exhaust mod.

Also one of my best friends locally has a 2002 996 TT that has exactly the same mods, stock exhaust, diverter valves and UMW that we bought at the same time. We have run the cars side by side during the whole process. Stock to stock, both cars were identical. I added the UMW first, walked away from him. He added his, identical again pulled side by side equally. SO I know that both are pulling the same, and not something awry with my car. Like I said on the street they feel strong with no hesitation.

But to make sure I am going to run him with race gas in my car on the street to make sure that the UMW timing is not too advanced for the 93 octane on the street (vs the Dyno with limited air flow). We should still be side by side even if I am running race gas and we are both on a 93 octane tune. We will see. If not, no problem, Kevin can just change the tune to 91 octane to match our local gas which very well may not be 93 as advertised, or may have methanol to get the 93 rating which does not perform as well as "real" 93 octane.

I know this is a long winded message and everyone is waiting for the results, but want to make sure it is right and Summer temps are an issue on the dyno so I need to schedule around the heat.

I sent the charts from my runs the other night to Kevin and he believes it is pulling back timing because of the lack of cooling. A 93 tune is what I requested from Kevin. He has been very informative and responsive and of course it happy to provide a modified tune to local gas if it is less than 93, Don't think I will need it, probably the dyno conditions, but that is what we are attempting to find out....Like I said the car feels great on the street.

Will post results, and will mod the exhuast once I get repeatable numbers.
 
  #38  
Old 07-06-2007, 11:41 PM
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Had a busy week at work but went to the dyno tonight (what a way to spend a Friday night... actually is fun to me..) This time went to get a clean curve on HP and torque. Dynoed again with fans better placed on intercoolers, sprayed the intercooler with water/alcohol to make sure they were cool before the run. Was about 80 degrees air temp. Car still showed a little timing pulling back above 5000 rpm on the dyno. Soooo I added some race gas, about 3 gallons, and I had a little less than a quarter tank of gas before adding the race gas. Run 4 was before race gas, run 8 is after. 461 HP and 434 Tq (getting rid of the spike in HP and drawing a line through the average of the curve it is closer to 450 HP, torque of 434 held pretty flat so no adjustment) I was expecting Torque to be higher and HP was right on what I expected. Remeber this is a stock exhaust car with only diverter valves and UMW software. (Dyno before the UMW was 388 hp and 401 tq on the same Dynojet)

Clearly at 5000 and above there is now a much stronger curve with the addition of the race gas. Keep in mind this is a 93 octane tune. I am assuming the dyno conditions and lack of fresh air compared to the street on the dyno is causing some timing retard. Next thing to test is to run on the street next to my friends car that has the identical mods except I will use the same race gas mixture to see if there is some timing being retarded on the street. As I mentioned before we both pulled identical with 93 octane in both cars. We will see if the tune on the street remains equal with race gas added to my car.

After I can verify that the real world street tune of the UMW for 93 octane indeed does run the same on the two cars, one with 93 and the other with race gas + 93 mix, then I will be more certain that the dyno conditions are causing the curve to fall when no race gas was used.

I will also then drill the stock exhaust and redyno (which is how this whole thread started). But I will use race gas mix to make sure I get repeatable results on the dyno.

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  #39  
Old 07-07-2007, 12:23 AM
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Great! Keep it coming!
The closest thing I ever came to this was trying to see if oil and trans additives would change my lap times when I was actively SCCA racing in the late 70s. I actually had a sponser and was hoping to impress them with my methodology. I did my baseline and then proceeded to barrel roll the car..... i can laugh now....

Thanks again for sharing this with us.

JR
 
  #40  
Old 07-07-2007, 08:09 AM
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Ok folks, we are about to find out the truth on this mod....in a scientific fashion. I propose we all make educated guesses on what the end will show....just for fun.

Facts: tt_tommy says he feels more power and earlier spool up.
I'll go first:

14 hp, 18 ft lbs of torque, earlier rise of both, with some slight loss of torque under 3k rpm (10% maybe) at worst. There it is, my guess.

It may be fun to get this on the site before Wooosh gives us the data.
 

Last edited by jcb-memphis; 07-07-2007 at 12:09 PM.
  #41  
Old 07-07-2007, 02:58 PM
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8whp. And it will still sound like a lawnmower.
 
  #42  
Old 07-07-2007, 03:39 PM
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I can tell you this, 8 -10 hp will be hard to see on a chart that is 450 or so. The electronics on our cars are so sensitive that they are constantly tuning during the dyno run. Hopefully with enough runs an average gain will show up.

Waiting to hear from Kevin on his thoughts about the Torque numbers and how adaptive his tune is to the race gas added.
 
  #43  
Old 07-07-2007, 03:57 PM
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Ran it on the street this morning with my friends that has the identical mods UMW, stock exhaust, DVs. Last time we ran 4th gear pulls only from 2500 to redline, no jumping, we were identical both with the same "93" octane. Now with the race gas added to my car from last nights dyno I pulled him by about a full car length. Which is not a lot but it was indeed different, and repeatable.

So not sure if the UMW software is adapting to the race gas or if it is pulling a little timing out on the street. Certainly the difference on the street is not as big as the difference that showed on the dyno. For example at about 5500 rpm on the dyno there was a delta of about 80-90 hp even thought towards 6500 rpm the hp curves got closer again. But 80-90 to the wheels would have pulled him by more than one car length. So I am guessing on the road the difference is a lot less dramatic, but there was a difference.

(It was about 82 degrees and humid when we ran, both cars cruzing first to make sure there was no heat soak on the intercoolers, etc.)
Sent this info to Kevin also and waiting to hear back on how his thoughts since I know nothing about his program other than the car feels good. Still baffled by the torque numbers.

I would love to see some other Dynojet charts posted for cars with just ECU upgrade and stock exhaust.
 
  #44  
Old 07-07-2007, 03:58 PM
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I'm guessing neligable and will be hard to detect.

tw
 
  #45  
Old 07-15-2007, 11:32 PM
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Stock exhaust mod

Well here we go, and all disclaimers apply...
The conditions were 97-98 degrees with 30% humidity according to the Dynoject weather module. Last time I ran it was 93.5 degrees and 40% humidity, both indicated a SAE correction factor of 1.04 so very comparable condidtions (but not favorable, would obviouly make more in cooler weather even with SAE correction thrown in).

Added race gas once again with 3 gallons of 110 added to 1/4 tank of 93 to make sure timing was not being pulled back on the dyno because of lack of real world airflow. This is the same mix I used last time (see earlier chart in thread labled run#8 in the previous chart which I have included that same run on the new charts.

MAde the holes in each side, used air powered tool with metal bit (see pic) worked great since drill bits would be difficult to use with extension since the hole needs to be made on the curve inside the exhaust. The diameter of the bit was about 3/4 inch, then once through the tubing I made the total hole about 1 1/14 in round like suggested in an earlier post that others tried. First impression, it sounds nice, mellow NOT weezey or tinny like I expected. It is not a replacement for an aftermarket sound in anyway, but it does sound a whole lot better than I expected, and is a little louder than stock.

Here's the scoop. It definately did NOT lose any power, and if you look at just the max number it did not gain any.....at peak. IT did however gain HP and Torque all the way from 3500 to 5500 rpm, More than can be ignored or discounted. In Run 10 it was the original size hole that it drilled above at about 1 1/4 in. In runs 11 and 12 I increased the diameter of the holes to about 1 3/4 in. Did not seem any louder but once again made a little more HP but gained in TQ. If you look at run 10 it only made about 10 more HP around 5700 rpm and was very similar to run 8 the majority of the run, and Torque was a little more than stock exhuast off and on, but never less. However after the holes were made bigger in runs 11 and 12, Torque jumped between 20 to 30 ft lbs to the wheels more that earlier runs, and stayed there between 3500-5500 rpm. My estimate from these charts are about 10-15 more HP between 3500-5500 and between 20-30 ft lbs in the same RPM range.

Above 5500 as you can see it went right back to where the orginal run of #8 shows. Guess is that once that much air is flowing it can't get out any quicker.

So you can believe it or not, but I am now a believer, and I do like the sound. I will at some point put on an aftermarket exhaust or make my own, because I do believe the factory exhaust is very restrictive and significant gains can be had with a good aftermarket exhaust.

I did not believe before my runs that there would be a measurable difference, but there was. I did my best to replicate the conditions, used the same gas mix, same fan placement, same dyno obviously, etc. So if you want a little more sound, are on a limited budget or just enjoy home mods, go for it.

I can tell you that I continue to be impressed with the UMW 1.0 bar flash, it is showing solid 459 HP to the wheels with stock k16's and K&N filter, thats it. I have other pics not posted here if you would like some more.

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Hole is bigger than it appears in this picture because it is about six inches inside the end of the tail pipe, it is about 1 3/4 in in diameter and the final shape is a little egg shaped on purpose to try to coax air to go that direction.
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