jss06c6

Kicking in new thread for this issue. Have a '91, 38,000 miles. Just completed SW headers, exhaust and Marc Haibeck reflashed my piggyback chip. Finally made it to the Dyno today. Results dissappointing. Made 241 rwhp and 244 rwtq. Last Dyno run was with stock manifolds, AIR and Flowmaster exhaust. Made 329 rwhp and 331 rwtq.

Believe issue is secondaries not opening at WOT in 4th on dyno. Have checked secondary vacuum pump operation, all good, cycles briefly every 5 seconds or so. Did electrical check on solenoids (pin 17 short to ground) and both sides close in 1 second, 100% travel.

1st, 2nd and 3rd appear to put good power to the wheels, but 4th is sluggish at WOT. Suspect secondaries are not fully open or open at all despite secondary vacuum pump apparently working. Thoughts appreciated. FYI, power key works just fine, green on full power and off when turned off. Driving in either condition (power on or off) shows no difference in power.

Dynomite

I am not familiar with your 91' but if all you modified was the SW and Air.....remove the piggyback from original chip and reinstall original chip to make sure it is not the Piggyback.

I have a Marc Piggyback on my 90' and as I recall the original chip is used with Piggyback attached. Marc started using Piggybacks recently as all my other original Chips were modified by Marc with NO Piggybacks. I could be all wet here as my 90' is in SD at the moment and I am in CA with my 91' that has a Stock Chip modified by Marc (No Piggyback). Or you bent a pin on the Piggyback....could be almost anything at the moment but if it got 329 rwhp before the SW and only SW and Piggyback modified...then Piggyback installation is the issue.

With the Stock Chip and no other modifications except SW...it may run a little lean but you should definitely feel the power.

scottfab

Put the stock (or as close as you have to stock) back in to get a baseline. If power comes back send the new chip set back to Marc for a check out.

If the the stock chip also fails to develop proper secondary power then keep them in to troubleshoot. It's good you verified the key etc. That is always the right thing to do.

Dominic Sorresso

Secondary vacuum pump shouldn't be cycling every 5 sec.

jss06c6

Going to pull plenum tomorrow. Will check all lines and vacuum cannister for leaks. Will clean up under there and change out any items that may be suspect. Sure hope its as simple as a vacuum leak!

Paul Workman

True, but NOT the AH HA! he's looking for. But! I agree - I too hate to pass up related stuff, just because it isn't causing the primary issue. Like so many...after my 2nd plenum dive to fix a secondaries issue, the third trip resulted in them resting in a cardboard box...forever more. (And, they haven't failed since!)

Dominic Sorresso

Paul,

I mentioned that as being indicative of possibly where to look. Not pointing to the problem.

Dynomite

Paul Paul Paul

I recall you have a 90'.....I did a top end on my 90' and wanted to experience that very unique function (the Power Switch) so restored the secondaries which now work perfectly. On my 91' I did eliminate secondaries just to simplify things under the Plenum

On Both the 90' and 91' I DID Eliminate the TB Coolant just because I did NOT want to experience Coolant Refilling every time I removed the Plenum

Maybe those NEW SW Headers caused the MAP hose to pop off on rear of Plenum....which would cause rough running engine at various speeds and maybe rough running idle also.

scottfab

I've heard that works with air filters too

I fixed my secondaries (and slightly modified them) in 99 and they've worked fine since. I did rebuild the pump again in 2010. Turned out to be a poor choice of rubber for the diaphragm that I used in 99. Used some cloth reenforced rubber as a replacement so we'll see.

jss06c6

Fixed.. problem was the checkvalve between the vacuum cannister and the plenum. I replaced it and moved it to be accessible just below the vacuum port on the side of the plenum. Secondary vacuum pump came up to vacuum and shut off, did not cycle. Buttoned everything back up and took it out on the road... all good. To test, I switched into full power mode in 4th gear at WOT and felt and heard the secondaries open up..

Thanks for all the help guys!

Dynomite

This was probably going on long before you recalibrated the Piggyback and long before you added the SW Headers

A case of too much information which messed up the cause and effect

You probably now feel power you never felt before and it is not the SW Headers

jss06c6

Agree that it was problematic before I upgraded exhaust. There was pretty good staining in secondary runners from fuel spray with nowhere to go owing to the butterflies not opening. Looking at the OEM manifolds and Flowmaster exhaust, I can guarantee the SW headers and the 3" SW exhaust make a significant improvement.

scottfab

If you live in a dirty and dusty environment that will come in handy having the check valve extended.
Your story of getting the secondaries to open up reminds me of my first ride after driving it home.
I gave a friend a ride (he has an 84) and it exhibited a bit more power than his. Then I got home and noticed the pump running constantly. As I check the hard plastic tube going toward the plenum I could feel a hole in the tube where it had been rubbing on the edge of an AC hose. Fix it and went back to my friends place and just said "get in". That ride was a bit different
What a rush that was.

illenema

Enjoy!!

jss06c6

Many thanks to the team! Looking forward to getting back to the dyno tyo see what she will do..

z06scentair

Awaiting Results......

jss06c6

Old thread, but wanted to post an update. I made it back to the Dyno today (yes, took me a while!) Recall my first trip had issues with secondaries, which I fixed.

Only made one pull today to check out improvements with SW Headers/Exhaust and Marc's tune to 93 octane and antibackfire. Engine was hot, temps today in Houston around 80 F. Car put down 345 rwhp and 349 rwtq compared to 241/244 running on only primaries on a cooler day @ 68 F. Best run with OEM exhaust manifold and flowmaster exhaust was 329 rwhp and 321 rwtq @ 73 F and cool engine. So SW Headers and full SW exhaust and a tweak for 93 octane added 16 rwhp and 28 lbft rwtq.

Can't help but think there's more in this engine without going in with performance cams.. Any thoughts on how much I might expect with a TB/Plenum porting job?

I'll be at the Texas Wannagofast run on November 13th. Hope to break 150 trap speed at half mile mark.. Will update on separate thread I have going..

G8nightman

I would say about the same gain you got with the SW goodies.

jss06c6

Going to launch a new thread on tunes for this setup.. Suspect the car is running far too rich.. AFR at 11.8 - 11.9..