so yeah its true...i switched over to tpi in my el camino to make it easier to pass emissions, but i managed to fail. first i would like to say that my egr is bypassed and so is my air system and also have 24 pound injectors. okay and the whole tpi system is a stand alone system with emissions deleted (larrys electic tpi harness). well my limits for hydrocarbons are 220 for idle and 2500 rpm, well i got a 852 on low and 253 on high rpm. also my limits for CO are 1.20 and i got .78 for idle and 2.88 for 2500 rpm. I was wondering what i should do, should i put smaller injectors in. I may need the timing set but im not sure what the timing is to be at. also i was thinking of running the air system back onto the car by retrofiting an older diverter valve that uses vacuum rather than computer. Would the air system make a good enough difference? please i need some opinions and also like to know what some people run with 350 tpis on the emission tests. now i have a month of a temp tag to get this thing fixed?????

 

The AIR system and the EGR probably won't matter. How old is the O2 sensor? Is it heated? Do you have a scanner? Is it running in closed loop?

 

First off with a swapped set up I’m going to assume it was tuned? As far as emissions is concerned without emissions controls it may be hard to pass without temporarily retuning for better emissions. However if you just want to get through put the air pump in and forget the diverter valve just have it dump air strait into the cat constantly temporarily. Not only will this give the emissions tester a false reading (as all those numbers are parts per million so putting more fresh air in makes the ratio better) it will also help the cat burn up more HCs. Although that being said i think you could do way better than that with a non emissions TPI set up especially in the low RPM HC area. However since You haven’t given any details on the motor and it seems your only real concern here is just getting though emissions it’s not something i will get into just something to think about.

 

Modern emission testers are smart enough to detect and reject diluted exhaust streams.

 

Quote:

Originally Posted by jv9999

Modern emission testers are smart enough to detect and reject diluted exhaust streams.

No there really not that smart. They do have pre set minimums and if you achieve less then the minimums they would expect they will fail you as they know somethings been tampered with to achieve thoes kinds of numbers but doing this will not push you under these minimums especially with numbers like that to begin with. I know because I have done this very thing (and not like 10 years ago just 6 months ago). You have to be pretty far under the maximums to fail. For example some of my best results with emissions tuning with a max of 800 NOX I’ve scored less than 200 and passed. CO2 max of .32 i scored .01 and passed. Both under the new "revised" emmissions testing.

 

well i have plugged up a computer system into my fuel injection and it does show it going into closed loop mode. the engine is a stock 350 tpi converted to speed density with no emissions and 24 pound injectors. nothing really special. im not exactly sure if the timing is rite so i need to know what the timing should be at and also is there a way i can tune this or do i have to find somebody that could do it cause im getting verry short on cash. also when i had the tpi with 19 pound injectors i would get so good of gas milage but now with the 350 and 24 pound im like wasteing gas soo bad. I dont really want to but if this tpi keeps giving me problems than im probly gunna take a switch to carb again. any ideas????

 

Well heres the thing although ECMs and stuff are all the same for a given type of ECM and are used on a wide variety of motor sizes the difference is in the PROM. The prom stores all the specifications for everything to be able to calculate how much fuel to inject. On a MAP system the way it works is to try and calculate the amount of air entering the motor using things like the MAP sensor and volumetric efficiency of the motor. This means that any changes to the motor that would effect the VE will throw off the ECMs ability to calculate the amount of air thats entering the motor causing your mixture to be off. Further more there are things like the injector size programmed into the PROM. The ECM uses this number to again calculate how long to turn on a certain size fuel injector to spray in enough gas to have the correct A/F ratio. So for example in your case its possible you have a PROM from a 305 system programmed for a 19 pound injectors and installing 24 pound injectors will make it way rich because the ECM is calculating the fuel injector on time for a 19 pound injector but a 24 pound injector will spray more fuel than the 19 pound injector for that same period of on time. Also the ECM compensates for emissions controls working. For example the ECM compensates for AIR system when its forcing fresh air into the exhaust manifold by expecting the O2 sensor to read lean because of the extra air that being pumped in. By expecting it to be lean the ECM doesn't over enrich the fuel. So as you can see changing things requires reprogramming especially on MAP systems. Especially in your case considering you have emissions deleted and if you have a 305 PROM running a 350 again it wont run right. So again long story short it all comes back to the fact you need to get it programmed to your specs whatever they may be. Now to tune it you cant do it yourself unless you have the equipment and since you ask i assume that you dont. You might be able to find someone local to do it or send your ECM or PROM in to a company like PMC for less and have them program it for you.

 

ok so heres where that problem comes in.....when the engine was swapped, i had a chip re burned for a 350 tpi with 24 pound injectors from the people who make the stand alone system. also today i hooked my laptop to the car and knowticed that i was staying in open loop mode and the air fuel ratio was staying rich so i put a heated o2 in and it went into closed loop easily and helped to keep the fuel ratio to 14.73, but it still smells a little on the rich side. also i set the timing to 10 degrees and which didnt really help with my jump from 19 to 25 degrees spark advance (i keep getting small spikes from 19 to 25 degrees every so often which sounds like a mis in the engine) now im not sure if this is ok to have or if this is normal. everything is stock but with a stand alone tpi with everything burned to specs. also no emissions on car at all except for charcoal canister for visual inspection. I only have one more shot to go back through inspection, im hoping i can find someone to tune the car, but im really out of money.