New Cat - New Problems, please help

[Emmo]

Hi, newbie here for the most part,

I'm having some trouble today with my Syclone. I had the truck inspected up here in Atlanta, GA for emissions and was thinking that the old cat wasn't maybe up to the task, however; I passed the emissions this morning because they didn't put it on a dyno and didn't check for NOx. Just a two speed idle test for CO2 and hydrocarbons. Guy said I was lucky to have the all wheel drive. But then the guy sold me on a new high flow catalytic converter despite only having ~22k miles on the odometer to replace the old one saying 13 years old, etc. etc. I'd been reading the forums and was considering a full 3" exhaust pipe instead of the two muffler so the ideas have been in my mind lately. Then I agreed and we put in a 3" cat on instead of the old stock 2.5" with the needed fittings and then back to the stock mufflers as part one I was thinking to see what performance I could feel. Anyways, driving along afterwards this afternoon, the truck seems fine until I get on the highway and gun it or really stomp the gas at any speed rolling along. Then all of the sudden the stock boost gage jumps to the 15+ mark and the engine quits until I let off the gas. Before with the old cat it ran strong all the time and I never pegged out the standard boost gage. Now I dont have a separate gage to confirm a pressure, however; I'm wondering if with the new cat and it's "supposed" high flow allows the boost gets too high for the computer and it cuts the fuel. Or could it be something else? I've check all my vacuum line and plug lines. Truck ran like a champ before the new cat. I went back to the shop and picked up my old cat and wanted to post here first.

I'm fairly new to the forums but have been reading alot. Curious if anyone has any remedies or suggestions,
Many thanks, Peter

 

[Flyin Ryan]

your problem is overboost.
it's very common on a stock trucks when the stock exhaust is messed with.

i'd say since your truck ran great before the new cat then it's the cat.. too much flow for the stock wastegate to handle and the computer can't provide enough fuel for those boost levels since it's 2bar or something like that.. anyway stick the stocker back on or try to adjust your wastegate to deal with the overboost.

http://www.syty.net/phpBB2/viewtopic.php?t=27190&highlight=overboost

 

[DanenGraham]

You are having an overboosting problem, the ECM cuts the fuel off after you go above 14.5#'s of boost for a prolonged time. The fuel cut is what you are having when the truck dies until you let off the gas. This has been covered many times before, you can search and find all the info you want.

Now you have two options, 1) take new cat off and get a normal non highflow to replace your new one. 2) you pull the turbo and port the Wastegate out to handle the new found power. (or just get a external and controler)

you can go ether way, option 1 will take you back to stock performance, option 2 will cost more but in the end your going to mod the thing anyway so might as well start now. :lol:



Edit, almost left out option 3. (ok i did leave it out) get a new 3bar chip that will add the fuel after 15#'s of boost, but you will still get very bad control if you still with the stock wastegate.

So, do options 2 and 3

 

[Sy769]

And do the first thing every syty owner should do. Get a good boost gauge.

 

[turbodig]

Re: New Cat - New Problems, please help

Hi, newbie here for the most part,

I'm fairly new to the forums but have been reading alot. Curious if anyone has any remedies or suggestions,
Many thanks, Peter

Everybody else's suggestions have merit, but a possible quick-n-dirty fix...

Turn your WG rod out 2-3 full turns (make it longer). This'll slow the rapid
boost increase you're getting due to the stock cat not being there.

Your second option would be to get a chip that's tuned to work with your
particular exhaust combo.

Also, as others have said, get an external boost gauge. I'm surprised there
are any out there still that don't have one....

Later,

Dig

 

[Emmo]

Thanks guys,

Yesterday I found and roughly got a new VDO boost gage intalled showing the full range. Now I can see a little more accurately what's happening. And sure enough fuel cuts out right at ~15psi. Now my biggest dilemna is deciding what to do now. I'd be really happy with just ~13-14psi using the stock ecm setup. From the readings and searches sounds like shooting for 13-14psi or right below the fuel cut off with the internal is like shooting for a moving target. Will try adjusting it this afternoon though to see what happens.

One question though:
It also sounds like the only way to go is to get an external ITS minigate flanged and welded to the crossover pipe just to be "safe". If I stay within the range of the stock fuel cutoff would the internal wastegate be sufficient? Or would going with a manual boost controller, Grainger or dawes devices type spring and ball or possibly an electronic unit, be "safe" enough to eliminate the need for the external wastegate. The truck is mostly a daily driver but started this idea of the new cat just looking for little more peep.

I do wish that I'd known what the boost peak was for certain before using the old cat. I'd be guessing around 10-11psi after comparing the new gage readings with the one on the dash.

Thanks again for all the help, Pete (it's actually a lot more interesting and involing dealing with a turbo than I'd expected. I like it.)

 

[Emmo]

Internal waste gate was / is extremely tight to cycle. Did stroke it a few times and seems better now. Took it for a drive and now can hear when it opens however it is so close to the fuel cut mark so I'm going to try a few turns.

One thing though, is there any tricks or tools for getting at or a hold of the rod? Sucker is super tight and know that I can't get at it with my small vice grips or plyers to really grab on a turn. Maybe a small small box wrench for the flats on the rod? Also afraid the pull the pin to spin it in fear of not getting it back in,

Thanks again

 

[Ian Turgeon]

Er, dont you HAVE to pull the pin, pull it off the wg arm, and turn it to change the length of the rod?

You might have to pull the inner fender well out to get it done easily. In fact, you may want to leave it out and go driving with a set of needle nose pliars, gloves, and adjust it untill you get the results your looking for.

 

[Emmo]

Update / Question

Got the inner covering off and pulled the pin to give the wastegate 3 full turns. Test drove it and it did seem to help especially on the street and below ~50mph, can't get it to overboost anymore. Runs really nice. However; on the highway it can still occur. Also have a feeling that the boost is now much less controllable on the highway even if I get this internal gate set right. It could start at 10psi and end up at the fuel cut off.
On the other hand I'm starting to get the idea that we're best stoplight to stoplight which is fine by me.

But I'm torn as to if I want to really start doing mods to this truck. I'm wondering if I could was to find an old crossover pipe and send it away to get a minigate installed on it. Or would you really need the muffler shop / fabricator to custom fit it between everything. I'm assuming either way they'd or I'd have to take off the pipe to get it welded up,

::thumbsup::

 

[Flyin Ryan]

Another idea on your overboost issue.. did you check your vacuum lines for cracks or holes?? I had a bad overboost issue a while back and found a small crack in a vac line right at the boost control solinoid which was the cause of my problems.