K R.....!!!

I have a 96 riv. with a 3.5 pulley ,2.5 down pipe 3in. magnaflow cat.
modded intake . ..I have a scan gauge to monitor timing and with just
a few pounds of boost 5 to6 pounds... timing drops to 5 or 4* and sometimes o*.....It' lost it's snap... fuel trim is - 6... 7 I changed the
fuel filter, checked pressure while driving.....69 pounds while into boost,
I changed the cat. , because it failed drive clean...to a 3in. Magnaflow..
flushed the injectors, installed fresh 104 did the seafoam clean, and still no luck....
any suggestions..... I always run premium....

Chuck norris Eats KR for breakfast.

what is KR spiking to?
thing you havent listed that can cause major problems are: wires, MAF and 02. are you throwing any codes?
its strange that you only have stock boost on a 3.5 pulley. is your BBV working ok? sounds like you are bleeding boost or not getting air through somewhere.

also, you posted this under series 1 engine and trans. you have a series 2 engine if it is a 96 s/c.

I couldn't run KR free on my 3.4 pulley until I added 1.9 rockers. You do need extra airflow mods to shrink the pulley.

Some cars have KR on a stock pulley. Did you scan before dropping pulleys? In a worst case scenario your lower intake manifold gaskets could be warped, interfering with airflow. But that's worst case...

You are still running stock manifolds?

Ive seen this way to many times to ignore. PUT YOUR 3.8" PULLEY BACK ON!!!. You need alot more breathing mods before you even think of running any smaller pulley.

i didnt know they made 2.5" DP's isnt that stock size?

Mr.Riviera wrote:

i didnt know they made 2.5" DP's isnt that stock size?

Stock is 2.25" IIRC

I have no codes.... the car ran strong before.....
this just started to happen.........It would run to 9psi , but I only run
it to a few pounds of boost........watching the timing......... not to
hurt it......
Could it be the fuel pump....?
What should the psi be at idle , or w.o.t. with the high speed activated....? any one run in to this....?

What kind of scanner do you have? I think you need a more complete scan to help us diagnose. Hopefully you got an MPS so you can bolt a stock size pulley back on there until you figure it out.

Bad gas maybe? Somebody throw some cheap fuel in it?

When did you put the 3.5 on?

When's the last time you changed your fuel filter?

Fuel filter was changed about 2months ago....
3,5 was on about about 8 years ago......
it ran strong before....

Check all your vacuum lines for starters... make sure the BBV is working all the way. Sounds like your FPR is okay. Bad gas? Try some octane boost and see if things change any. Maybe accidentally filled up with E85?

BBV........ is that the waste gate ... vac. lines ok ....
replaced some already..... and we don't have E85 around my
area..... I'm thinking its fuel related , pump or pump module.....

2.5" DP exists - it's made for NA 3800 engines. SC engines should use 3" DP.

I had lots of KR before changing my injectors. I used injector cleaner many times, but after so many miles they may need replaced or professionally cleaned. How many miles on the car?

2.5" pipe is fine for s/c or n/a. Why would you put in a 3" DP only to route right back into 2.5"? Seems kind of pointless unless you have all 3" exhaust piping.

Rick you should really put a stock pulley back on or at least get a plog.

The muffler shop couldn't make the 3.0 inch
The owner has a gtp with a 2.5 dp and says it dynoed at
375 hp........and said it was plenty....
I have about 249.000 km.....on it....... which is about 130 ish miles
How long do fuel pumps usally last.......or injectors...?

Quote :

2.5" pipe is fine for s/c or n/a. Why would you put in a 3" DP only to route right back into 2.5"? Seems kind of pointless unless you have all 3" exhaust piping.

Some have reported changing only the DP to 3" gives a nice HP gain. Also, putting headers on a totally stock exhaust provides a nice gain. I still have stock cat-back. The stock Riviera exhaust is a better design than W-Body, imo.

Rick, I swapped my injectors at about 165k miles. Made a huge difference. Ordered refurb from RockAuto for cheap.

AA wrote:

Quote :

2.5" pipe is fine for s/c or n/a. Why would you put in a 3" DP only to route right back into 2.5"? Seems kind of pointless unless you have all 3" exhaust piping.

Some have reported changing only the DP to 3" gives a nice HP gain. Also, putting headers on a totally stock exhaust provides a nice gain. I still have stock cat-back. The stock Riviera exhaust is a better design than W-Body, imo.

Rick, I swapped my injectors at about 165k miles. Made a huge difference. Ordered refurb from RockAuto for cheap.

There is nothing wrong with the cat-back exhaust on the w-bodies. There are 11 sec gtp's on stock cat-back, nothing is really restrictive there. What i mean is he still has stock manifold's those choking primaries. So if you have those restrictive manifolds squeezing into a larger 3" dp just to go back into 2.5" piping it just seems pointless to me. Headers are a whole different ball game. With headers you have better flow coming off both heads, which is why the gains are great.

99prixgt wrote:

There is nothing wrong with the exhaust on the w-bodies.

...U-bend?

edited- cat-back The U-bend is on the downpipe not the cat-back itself.

True, headers are a different idea. But that benefit isn't negated by the stock exhaust. The argument for a 3" DP is fluid dynamics:

Bernoulli's Principle states that as you decrease tube diameter, pressure inside the pipe decreases, increasing velocity of the exhaust gas. So smaller diameters flow faster than large ones.

Exhaust gases cool off more quickly the longer they stay in the exhaust pipe. If you use too big a diameter, the gas moves more slowly, so becomes cold (and dense) before it leaves the system. This is bad, because the gas itself is forming a blockade. This is why why we wrap header tubes - to keep the gases hot and moving fast. Smaller diameter pipes do the same thing.

I understand the blower is creating the pressure to push exhaust through, but It's not always bad to taper exhaust tubing. Not saying a totally open exhaust wouldn't be better for HP, I'm just making an argument that a bigger downpipe is still a plus by itself, because the rest of the exhaust system isn't as restrictive as it might seem.

The reason I think our exhaust is better than W-Body's is because of the lack of bends - it's a long straight that helps cool the exhaust gases. Deleting the cat also helps this a lot.

AA wrote:

True, headers are a different idea. But that benefit isn't negated by the stock exhaust. The argument for a 3" DP is fluid dynamics:

Bernoulli's Principle states that as you decrease tube diameter, pressure inside the pipe decreases, increasing velocity of the exhaust gas. So smaller diameters flow faster than large ones.

^ yeah they flow faster but that doesn't mean you will gain hp if you get really small piping for alot of "flow" then there will be too much back pressure, and no hp's and your car will run horribly.

AA wrote:

Exhaust gases cool off more quickly the longer they stay in the exhaust pipe. If you use too big a diameter, the gas moves more slowly, so becomes cold (and dense) before it leaves the system. This is bad, because the gas itself is forming a blockade. This is why why we wrap header tubes - to keep the gases hot and moving fast. Smaller diameter pipes do the same thing.

^ Irrelevant statement. The argument was for small-larger-smaller exhaust piping makes HP. There wasn't any talk of wrapping headers, but I will add that this is why when people wrap their small exhaust manifolds and sometimes plogs they will crack because, the hot exhaust gasses have no-where to go.

AA wrote:

I understand the blower is creating the pressure to push exhaust through, but It's not always bad to taper exhaust tubing. Not saying a totally open exhaust wouldn't be better for HP, I'm just making an argument that a bigger downpipe is still a plus by itself, because the rest of the exhaust system isn't as restrictive.

^ still your stock exhaust manifolds are and yeah its not "bad" to taper as long as it's not to a certain extent but, it won't make HP either. Big turbo applications will benefit from no exhaust a.k.a open waste-gate.

So basically all your statements are irrelevant with the original statement which was smaller to larger to smaller exhaust piping makes HP, which is what this "tech" discussion started as.

I actually have a scanner up for sale if ya need one!

Rick's Riv wrote:

The owner has a gtp with a 2.5 dp and says it dynoed at
375 hp........and said it was plenty....

I'm calling BS on this one, unless your muffler guy is one of the few 3800 specialists out there... if he were really pushing 375 he'd be running headers. Maybe MAYBE 275?

375 takes a HELL of an engine build, and there's nobody I know of who would put that much money into an engine build and not come out of it with headers.

Show me the dyno papers and I'll humbly eat my words, but I highly highly doubt 375.

375 is what he told me.....It's got lots of modds
cam , head work, ported stock manifolds , ported blower.....
The shop deals with the Honda crowd........ Maybe Its in
Hondahorsepower........LOL

Rick's Riv wrote:

375 is what he told me.....It's got lots of modds
cam , head work, ported stock manifolds , ported blower.....
The shop deals with the Honda crowd........ Maybe Its in
Hondahorsepower........LOL

It's certainly possible, I'm just surprised that with that much work he wouldn't opt for headers by that point.

I know there is a good sized crowd that says PEM/PLOG is good enough... but still 375 is a tall order...