| Author |
Message |
HaK (Howard)
New member
Username: Howard
Post Number: 30
Registered: 4-2002
| | Posted on Saturday, May 24, 2003 - 5:44 pm: | |
Thanks Gary finally a black and white answer. I am putting the cats back in next week. |
Ben Millermon (Brainsboy)
Member
Username: Brainsboy
Post Number: 325
Registered: 5-2001
| | Posted on Friday, May 23, 2003 - 1:35 pm: | |
rob I posted before I could finish, I know you agree its lean but you said its burning off extra fuel in the exhaust. If the popping is coming from unburned fuel in the exhaust why would adding more fuel solve the problem? |
Frank K Lipinski (Kaz)
Member
Username: Kaz
Post Number: 309
Registered: 11-2002
| | Posted on Friday, May 23, 2003 - 1:28 pm: | |
Jim -
Way cool car. Absolutely stunning!
BTW-now that DES has a dig cam this site will never be the same... |
Ben Millermon (Brainsboy)
Member
Username: Brainsboy
Post Number: 324
Registered: 5-2001
| | Posted on Friday, May 23, 2003 - 1:27 pm: | |
Rob I had the same problem with my 308 a few threads below this. If it is unburned fuel causing the problem then why did the popping go away when I richened up the mixure on my car? I think its due to a lean mixure. 60% of my popping went away when I richened up the fuel mixture. My car is not a 355 but the theory is the same. |
Gary Reed (Gary_reed)
Junior Member
Username: Gary_reed
Post Number: 86
Registered: 2-2002
| | Posted on Friday, May 23, 2003 - 1:09 pm: | |
Howard,
If you don't like the sounds that your exhaust is making, just put the cats back in. They will eliminate the popping sounds. |
James Glickenhaus (Napolis)
Intermediate Member
Username: Napolis
Post Number: 1398
Registered: 10-2002
| | Posted on Thursday, May 22, 2003 - 10:29 am: | |
My Duesenberg had this technology 71 years ago. A cockpit controlable lever allows you to increase exhaust back pressure for more low and mid range torque and even engine breaking if you wany it and another cockpit control allows you to vary engine timing. The dashboard altimeter is usefull in using the carborator enrichment lever as well.
You must still remember to wind the clock every 8 days...
Pics in Des WWOC I post
http://www.ferrarichat.com/discus/messages/21/251598.html?1053540296 |
Frank K Lipinski (Kaz)
Member
Username: Kaz
Post Number: 301
Registered: 11-2002
| | Posted on Thursday, May 22, 2003 - 10:15 am: | |
Rob - you are right on the bullet! |
Rob Schermerhorn (Rexrcr)
Member
Username: Rexrcr
Post Number: 591
Registered: 11-2002
| | Posted on Thursday, May 22, 2003 - 7:13 am: | |
HaK,
The popping on deceleration, closed throttle with no catalyst or muffler, in general, is not cause for concern. Enjoy the show, this is race car stuff! It's unburned fuel igniting in the exhaust, in your case, it's okay, BUT.....
You have certainly decreased the exhaust system pressure and changed flow characteristics. You are probably running lean under some or all conditions (throttle position, rpm and load variations).
To optimize your new system, you need time with a data logger, a chassis dyno or open road, a UEGO wide band oxygen sensor (big bucks, though Bosch builds one that's not as fast responding for less), and an experienced engine management tuner. You will find the power you lost (by leaning out your engine) adding fuel in certain specific events in the fuel map. Just buying a generic chip will waste your money.
Have fun with the new HP! |
BILL CHIUSANO (My355)
Junior Member
Username: My355
Post Number: 102
Registered: 3-2003
| | Posted on Thursday, May 22, 2003 - 12:46 am: | |
I HOPE MY355 STARTS SHOOTING FLAMES OUT THE TUBI'S!!!
MY355 |
Bruno (Originalsinner)
Intermediate Member
Username: Originalsinner
Post Number: 1132
Registered: 5-2002
| | Posted on Wednesday, May 21, 2003 - 9:27 pm: | |
normal occurence. Wouldnt adjust a thing. |
Kelly (Tifosi1)
Member
Username: Tifosi1
Post Number: 626
Registered: 2-2002
| | Posted on Wednesday, May 21, 2003 - 9:13 pm: | |
When it backfires, does it shoot out a flame??
Example. an F50 I followed at a rack event would shoot out about a 3 to 4 foot flame every down shift. No race gas either.
Great site and sound, i would not complain.
My 2 cents,
Kelly |
JRV (Jrvall)
Intermediate Member
Username: Jrvall
Post Number: 1512
Registered: 11-2002
| | Posted on Wednesday, May 21, 2003 - 9:12 pm: | |
>>If it does help, why haven't auto manufacturers found a way to use it to an advantage? <<
They have, Vario Ram Intakes and Vario Cam Timing. Increases Torque on the bottom and Breathes Freely on the top. Super Trap believes in Pipe Tuning also for Top end or better pulling off the corners. Or a compromise. |
Matt Morgan (Kermit)
Junior Member
Username: Kermit
Post Number: 135
Registered: 8-2001
| | Posted on Wednesday, May 21, 2003 - 9:05 pm: | |
I must agree with Art, in that what is happening is a lean condition. I have seen this, and find it to be caused by the improved exhaust flow causeing the motor to be able to pullmore air thru during deceleration. Problem being, it isn't getting more fuel with that air if adjustments aren't made to the system. And haveing been involved in many types of racing, have seen exactly what Ben describes. Simply opening the headers will often hurt low end performance. But if a header extension is added, low and midrange is much improved. A track tip there is a longer extension, the lower the torque curve is, to a certain extent. This can be an invaluable tip in tuneing for a particular track. Henryk and I agree on this as I have not heard a valid technical explanation how it helps. If it does help, why haven't auto manufacturers found a way to use it to an advantage? It would not have to be any more complicated than a simple butterfly valve in the exhaust. It could be tuneable, and the production cost would be low. I'm open to any input on this one as I have listened to and been part of that arguement for years in many areas. |
Ben Millermon (Brainsboy)
Member
Username: Brainsboy
Post Number: 320
Registered: 5-2001
| | Posted on Wednesday, May 21, 2003 - 8:39 pm: | |
JRV is right. I know it doesnt make sence but, back pressure does help produce more torque and low rpm power. I have seen alot of guys at the track take off the exhaust and run slower quarter mile times. |
JRV (Jrvall)
Intermediate Member
Username: Jrvall
Post Number: 1510
Registered: 11-2002
| | Posted on Wednesday, May 21, 2003 - 8:18 pm: | |
>>What is all this talk about "backpressure"? Why would anyone want it.>>>
Low end and mid-range backpressure helps increase torque.
Torque is your friend. |
Henryk (Henryk)
Member
Username: Henryk
Post Number: 714
Registered: 8-2001
| | Posted on Wednesday, May 21, 2003 - 8:08 pm: | |
What is all this talk about "backpressure"? Why would anyone want it. The idea is to get rid of the exhaust gases fast, and backpressure will only hinder this.
Backpressure, from quiet exhaust, or cats, is only the consequence of having to have these items. These items are restrictive in nature, hence, the backpressure.
But WHY would you purposely want it? I don't understand. |
Frank K Lipinski (Kaz)
Member
Username: Kaz
Post Number: 300
Registered: 11-2002
| | Posted on Wednesday, May 21, 2003 - 7:29 pm: | |
Howard - Art may be correct, But what you are hearing may be the result of the Tubi itself and is the reason I have not gone with it myself.
I've experienced this on other cars (P-Turbos) where I pulled cats and did other mods to the exhaust. Also, when I was considering Tubi for my car I did a search on the same subject and found many threads stating the same.
The Tubi will allow the exhaust to flow freely and generate more HP. However, the "freeflow" will decrease backpressure and unspent vapors will exit as well.
Most cars will backfire / pop slightly but the sound is surpressed by the muffler. The less restrictive the muffler the more noticable the popping.
Usually it is most pronounced during downshifts or between the upshifts (coming off the gas).
Do a search on backfire / tubi ..
FL |
arthur chambers (Art355)
Intermediate Member
Username: Art355
Post Number: 1733
Registered: 6-2001
| | Posted on Wednesday, May 21, 2003 - 7:06 pm: | |
Mixture too lean. ECU adjustment needed.
Art |
HaK (Howard)
New member
Username: Howard
Post Number: 29
Registered: 4-2002
| | Posted on Wednesday, May 21, 2003 - 5:48 pm: | |
Couple weeks back had fitted to my '95 F355 Tubi test pipes and silencer. Happy with sound etc but engine is backfiring and popping when coming off the gas pedal. Any ideas how to cure this? |