2.5" DP and Magnaflow--RESULTS UPDATE - Page 4 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-13-2007, 12:12 PM   #31
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That'* good to hear...

The original gains seemed a bit overstated for the changes made. 4-5HP and torque is respectable from a mod like this and great to see.
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Old 08-13-2007, 12:27 PM   #32
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I have to agree, every little bit counts on a NA setup.
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Old 08-13-2007, 02:40 PM   #33
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As promised, here is the latest VE graph:


The 2.5" DP and Magnaflow cat show an increase in calculated VE across the entire range, but with diminishing return above about 5k rpm.

Here'* the new latest calculated improvements vs mod levels:

Mod Level---Torque (@4200rpm)---HP (@5200 rpm)
Stock-----------+0 ft-lb--------------------+0 hp
PLIM------------+10 ft-lb-------------------+8 hp
PEM-------------+6 ft-lb--------------------+5 hp
L67TB----------+16 ft-lb--------------------+17 hp
SRR-------------+4 ft-lb---------------------+9 hp
DPCat-----------+5 ft-lb---------------------+4 hp

For an estimated total of about +41 ft-lb @4200 rpm and +43 hp @5200 rpm over stock (or at least, over where I started from :P ).

Again, having bought alot of hard parts used, I'm now about $450 into parts/gaskets with what'* charted above.
That'* just over $10/hp (if my calculations are close), so I'm happy so far.

(As always, these are calculated estimates only, not yet backed up by actual dynos...)

The exhaust is louder and "throatier" than before, probably because the new DP is a single-wall (instead of a double-wall like stock). For the most part, I like it...but there is a slight "droning" sound between about 2500 and 3000 rpm that I could do without, and start-up in the driveway in the morning is louder. Should this DP ever temporarily be removed for any reason , I'll probably use some header wrap just to try to muffle it a bit.

As I've mentioned before, something'* severely holding back the upper-end performance (above 5k rpm), and it'* likely the restricted intake tracts in the stock L36 heads:
http://www.bonnevilleclub.com/forum/...ic.php?t=77163

Modded heads (and better valvesprings) are down as a winter project, so I'll probably work on some low-cost UIM modifications between now and then (kinda modeled after zzp'* HV inserts; TJ and BillBoost know what I'm working on).

If the head work pans out the way I'm hoping it will, the rest of these mods will probably synergize very nicely with them. If the head work doesn't give me what I'm looking for, I'll have to give serious consideration to some stronger medicine
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Old 08-13-2007, 02:49 PM   #34
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once the car is running decent.... I will be doing some before and after testing on your HV3.247389 project
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Old 08-13-2007, 08:13 PM   #35
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well that good to know because i still have the stock down pipe .i think that the next thing to take care .andrew are youre PEM welded or just ported
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Old 08-13-2007, 09:03 PM   #36
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Quote:
Originally Posted by firebuick
well that good to know because i still have the stock down pipe .i think that the next thing to take care .andrew are youre PEM welded or just ported
Remember, I have the "fake" front ported exhaust manifold...no welded-on material on the outside.

I may step up to a PowerLog (v2) someday...like this DP/Cat, that can easily be swapped for stock when necessary.
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