Is there a quick way to prevent the turbos from pressurizing? I am trying to pass emissions and was advised when the car goes into boost it runs rich. When I bought the car several check valves/vacuum lines were not connectd or broken, the boost gauge tap on the UIM was uncapped, and the pre-cat was installed. The cars turbos did not seem to spool under this condition. Since i repaired the vacuum lines the car is much faster. I presume the precat was the main reason it passed before but it had to go. I also think not having full turbo function helped. Any idea which vacuum hose I can discretely and quickly de-couple for the sake of an emissions test?

Hydrocarbons: 1.4 over 1.2 limit
carbon monox: 45 over 15 limit

That was with 91 EtOH free gas - I am going to run 85/91 octane mix on my next go to get some ethanol in there.

 

Without the pre-cat, one thing that may help is to be sure that the engine is thoroughly warmed up before testing. Run it for at least 30 minutes.

 

If you just want to disable the turbos, loosen one of the intercooler hose clamps. Zero boost in no time.

Dale

 

OP are you running an IM240 test cycle? Like the car is actually driving a vehicle speed trace on a dyno? Or is it running steady speeds like 15mph and 25mph?

The easiest way to stay out of boost on an IM240 is to get a different technician to drive the car. The guy driving probably has a lead foot. They can drive it easier and not fail the test as long as it's within the vehicle speed vs time limits (basically, a min/max acceleration during the drive).

 

Yes it is IM240 and there is no requesting your tech; you just get who you get and they probably relish driving a car like mine, break up the monotony of minivans etc.

 

Can you explain your full engine mod list? Stock ECU, stock cat, working air pump?

 

Disabling the charge control flapper on the back of the ypipe would cause almost no primary boost.

 

Car is OEM except for a downpipe, all systems are functional. I do have a 2002 JDM air intake duct which pulls air from the front bumper cover instead of the intercooler ductwork. However, there is no ventilation into the bumper cover and I am perhaps starving the engine and forcing even richer conditions?

The car likes to backfire a lot.

 

That intake should make very little difference.

If it's popping a lot there are troubleshooting steps in the shop manual for "afterburn" - could be any number of things. These cars do pop some anyhow.

Dale

 

Does the car have any stored check engine codes?

 

Nope - runs like a top.

 

I've never been clear about how altitude affects these cars, but I think Denver being at 5,000 ft might make it run richer than if you were at sea level if the car can't fully compensate for the thinner air. On the other hand, the cold air this time of year is denser, so the mixture would be leaner than in summer temps.

 

Stock ECU has an atmospheric pressure sensor built into it, it should compensate enough

How many miles are on the cat, and do you still have a precat? Can you post the document they gave you after it failed? There should be an emission trace showing where it's producing the emission. Do you know if the car sat a while before running the trace? If it's just going rich on accelerations, we should see it in the emission trace.

See this thread and post where a guy was trying to pass an IM240. https://www.rx7club.com/3rd-generati.../#post11954241

 

boom

 

Thanks for the link! I will look into that thread, should provide some good info. My car has 50k on it and it's all original.

 

You’re failing at 155 seconds when it goes into boost. See how the CO pegs the limit twice, dropping in the middle? That could be the secondary turbo coming on. It’s Too much throttle and/or needs to up shift early and lag the mph trace a bit.

To be honest I’d try shopping around for different inspection stations or going on a different day to get a different driver. Also try unplugging the precontrol and wastegate solenoids to drop the boost. I don’t remember if that causes an immediate CEL or not. If so, try putting resistors across the terminals

 

I really appreciate you looking at that with me. Do you think un-coupling at the intercooler/charge pipe to TB would 'unboost' the engine without risk of a CEL? My drive was a 18-21 year old kid and I could hear the car boosting. Unfortunately not much I can do about that except mechanically disable boost.

 

It’s worth a try.

 

Had a friend who forgot to tighten an intercooler coupler, came over and was "why isn't my car making boost?"

It seriously was like driving a non-turbo, no noise, no anything weird, just no boost. Big enough boost leak will do that.

I'd try that first, it takes 5 seconds and is easily reversible and easy to test.

Dale

 

I used to work on some failed Denver smog FD RX-7 long ago. The driver has a massive input on the readings. You need a gentle driver. On close cars you can remove the air pump relay and jumper it so it runs all the time. This way when the RPM goes over 3200 it still pumps air and lowers the emissions a bit. Check your idle vacuum. If it's lower than 14" at idle the car starts to run rich and Denver is difficult. Turn off all loads.
sorry for the double post

 

I used to work on some failed Denver smog FD RX-7 long ago. The driver has a massive input on the readings. You need a gentle driver. On close cars you can remove the air pump relay and jumper it so it runs all the time. This way when the RPM goes over 3200 it still pumps air and lowers the emissions a bit. Check your idle vacuum. If it's lower than 14" at idle the car starts to run rich and Denver is difficult. Turn off all loads.