3" Vs 3.5" Downpipe?? Help!

J

juanjo322

Member
Joined
May 6, 2005
Ok.. well some of you may or may not know that I am in the process of buying one our fellow members T Type, However we have been back and forth on a downpipe. The car currently has an 3.5" internally wastegated downpipe and we were discussing on getting a 3.5" Externally wastegated downpipe.. I don't know the first thing about this.. can anybody please help me on the benefits on whether or not 3" 3.5" internal/external wastegated DP. All help is greatly appreciated.


Thanks for looking.


Juan
 
Juan,

you don't have to make any changes unless there is a boost control problem with the car. The only reason to switch to an external gate is to use a boost controller (takes an external gate type setup to work right) or to help control boost - because a properly sized external gate can be used to turn the boost down more if needed.

If you can get your boost down to where you want with the internal downpipe on it.. then leave it alone.
 
ETicket,

Here is the list of items, I remember your post on Cody's thread about how nice of a car it is.. here is the spec sheet JIC. On the same note I will add that Cody has mentioned that the car does have " don't quote me on this " a 2 stage boost controller, he mentioned that downpipe is ok.. but that he has noticed the boost sneak up and well he thinks and I agree that I should consider an externally wastegated DP. On your post you hit the nail right on the head.. It does seem to sneak up and therefore the question? I am having a hard time getting a very nice used one.. they are pricey, I saw one here not too long ago but it's a 3" DP with Ext WG and Dump pipe.. just don't know whether or not to go for it.. I am afraid of losing performance if you know what I mean..

Performance:
234ci
109 block
.30 over Diamond Pistons
RJC Girdle
K-1 H-Beam Rods(floating)
Cat Crank(stock stroke)
Center Billet Caps
King Bearings
Hi-Volume oil pump
RJC Crank Scraper
JW(the wheel) flexplate
BHJ(internal) balancer
Port Matched Stock Intake
218/218 Hyd Roller Cam From DLS
918 Beehive Valve Springs
Comp 853 Lifters
Chrome-Moly Push Rods
Champion Ported GN1 Alum heads(porting done by Nick Micale)
70mm Throttle Body and Matching PTE Plenum
F.A.S.T XFI with 83lb injectors(including laptop)--from Cal Hartline-he helped me tune it
Full RJC Alum Pulley Set
PTE Front Mount I/C(new design)
TA Stainless Headers
PTE 70GTQ Turbo(3 bolt)
HRparts poly motor mounts
RJC Zinc plated deep sump oil pan
Full Billet 200r4 w/ Transbrake
Pats Perf. 10.5 L/U 3800 Rated stall converter
Denny's Nitrous Ready Driveshaft(all 1350 series w/ chrome moly trans yoke)
Moser 30 Spline Axles
Detroit TrueTrak Posi
TA Rear Girdle
3.42 Gears
FULL HRparts Rear Suspension with ajustable sway bar and control arms
Competition Engeneering Front and Rear ajustable shocks
S&W 8Pt Roll Bar
Aeromotive A1000 Fuel Pump
Alum 15 Gal Fuel Cell in trunk with sender(gas gauge works)
Fiberglass Front and Rear bumpers/bumper fillers just went on
Alum Bumper brackets
Has Dual Electric fans
3.5in Internal Gate Downpipe w/test pipe
3.5in Electric Cutout
B&M Quicksilver Shifter
ATR Dual Stainless 2.5 Exhaust(with Stainless Dynomax Mufflers)
Autometer Phantom pillar (0-35) boost gauge and (3-3/4) Tach
Kirkey racing seat on drivers side-grey color to match interior
RJC 5pt harness for both front seats
 
I know Cody's car well enough and know your issue.

The only real fix to bring the boost down for you, probably, is to put an external wastegate on that dumps off of the headers. You can do this "nicely" by adding on to your headers and replumbing back into the system.. or just adding one to the xover pipe and be done. Just depends whether you care if the car is noisey under power.

A simple external gated downpipe will not do the job.

You will not gain or loose any power doing any of this.. this is all to turn down the power for street use.. not to turn it up.
 
Thank you for your response, I dont think i need to turn down the power and about the noise well, i drive a diesel with silencer ring removed and dont think there is any better sound in the world than the whistle of a turbo. I dont know if you have checked the thread but the block is done!!! Cant wait.... such good news.

I appreciate your response and this will be perhaps my last message for the night as my wife and i just had our 6th child! a beautiful baby girl, Isabella Hernandez my blessing came as a double :)



-Juan
 
I am going to a custom 3.5" downpipe so I have a ATR 3" downpipe setup with external Deltagate (wastegate) for sale. I also have a high flow cat for it. Shoot me a PM if interested?
Hot Air
E85 Moderator
 
Hot Air said:
I am going to a custom 3.5" downpipe so I have a ATR 3" downpipe setup with external Deltagate (wastegate) for sale. I also have a high flow cat for it. Shoot me a PM if interested?
Hot Air
E85 Moderator
Click to expand...


Hot Air,

This response is long overdue and for that I apologize, I or we (Me and Cody) are going to go ahead and get the 3.5" DP from Mark @ BuickGN.com. Thanks for the offer but I seriously didn't want to go to a smaller DP.
 
juanjo322 said:
Hot Air,

This response is long overdue and for that I apologize, I or we (Me and Cody) are going to go ahead and get the 3.5" DP from Mark @ BuickGN.com. Thanks for the offer but I seriously didn't want to go to a smaller DP.
Click to expand...

I got my 3.5" DP from Mark... Very nice you'll be happy with it.
 
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