Dark Blue Cat

Well.. I had a look under the truck and saw the Cat was various shades of blue. I gave it a little shake and I thought I heard a rattle.

I figured it was broken inside, or I cooked it, so i cut it off to have a look in.

Turns out I can see through it, but it looked like a little bit of sand came out of it.

I don't have to get a emission check where I'm at, so I COULD replace it, or leave it off. As i decide, I put a piece of pipe in it's place.

Things I noticed without the cat......
1. its a lot louder through the muffler and the sound is deeper.
2. With cat, the truck stopped pulling at 4200 rpm, now it will rev to 5000 rpm (barely)
3. Idle vacuum is up to 18 in (with cat it was 15) but driving vacuum at 90 km/hr is still 10 in and under (which isn't good)
4. No idea if mileage is better. I filled up today so I will see
5. For some reason, the transmission shifts higher (not shipping manual) although I did not adjust the kickdown cable!!!
6. A lot more popping when I lift off the gas pedal (maybe it did it before but i didn't notice it cause the cat dampened the sound)

Any ideas?

The cat sounds like it had collapsed internally. It was clearly acting as an exhaust restriction which explains the blue colour from getting cooked (they aren't supposed to get super hot to burn polluting components in the exhaust gases as they rely on a chemical reaction - melting the converting matter will clog it up) You've probably gained torque as well which will alter how the engine loads up the auto trans (hence the shift rpm change) The exhaust pulse is now travelling the full length of the exhaust and will scavenge gases from the exhaust ports more efficiently which is why you're getting the 'popping' off hard throttle.

If you mess with ignition timing you should get improvements in vacuum and overall power - there is hidden power to be made by regapping the plugs, using premium fuel and dynamically adjusting the distributor timing (no timing light needed but you will need a dwell/tach meter to monitor engine rpm's) Remember to get the ECU into tune/diagnostic mode to adjust the timing.

I adjusted the timing for peak Vacuum last year and never thought to do it again. Great idea.
I run a vacuum gauge in the truck just so I get an idea of how much throttle I was using to run a certain speed.
I will try that and see how it helps.

I will report back on what i find.

Remember this truck has 270K KM (167K Miles) so I can't expect miracles.

Next week is Mopar day and it will be interesting to see if i can get this underpowered turd into the 18's...LOL

Yeah it could probably do with a set of fresh rings and the bores deglazed. That will restore some power (you can get away with it if the bores don't have significant wear). It should be generating more vacuum than that so it is more than likely getting tired. The ignition coil needs to be in good shape to so it will maximise air fuel charge burn. Check the air filter is in good shape too - you'd be surprised at what difference running a dirty filter can make compared to a fresh one. What I do for ignition tuning OBDII is this - regap plugs to 0.85mm, hold engine rpm @ 2000 and swing the distributor between advance/retard until rpm's spike by itself, back off a touch and lock the distributor up. It should pull through the rpm range and get to gear changes faster. It's best to add a premium fuel (I find 90 octane makes a difference - above that it doesn't seem to make a difference for non performance engines) I run the Australian equivalent 95 in my cars and compared to regular fuel I'm lighter on the throttle and it makes more torque. I also add 250mL of synthetic 2 stroke oil for every 20L of fuel to keep the upper cylinder lubed (when I can...)

*I noticed that ethanol is added to ALL US gasoline fuels now. Not good for engines not designed for it... :shakehead:

ya'll are prob beyond this but I don't have a cat on my 86 automatic anymore and it runs and sounds way better. (my cat had totally melted)

I agree it is tired. I was thinking about a re-ring of the block.. remove the balance shafts and through on the ported head I am working on.

Filter is in great shape and removing it at the track made it a tenth of a second faster..HA HA HA

Tonight I adjusted the timing and now it pulls to 5000 rpm in each gear.. it never ever did that in 5 years of ownership.

The coil is an aftermarket... that was the first thing I changed as the original one cooked itself.

Butt dyno says i might just get into the 18's.

I figure a re-ring would certainly help this little motor have a little life.

is your motor a 2g or 1g motor? i know your truck is a 1991 but check the front of the oil pan. bumped out means its a 2g. if you have a 2g than instead of putting original pistons in you could put a set of pistons from a 1999-2003 eclipse 4g64. they are flat tops. would give you a bump in compression.

Ported head, fresh rings, remove the factory clutch fan = better throttle response. Make the intake longer with a feed from outside of the engine bay = more torque. 2 stroke oil in the fuel decreases upper cylinder friction = cooler engine, more torque, added throttle response (be really conservative with 2T synthetic oil as a little will go a long way) Little things have a cumulative effect :thumbup:

I haven't run the stock fan for about a year. I have it on a switch and actually rarely need to run it at all. Next year when I swap to a Holley Sniper and Turbo I will have it control the fan.

I will look at whether it is 1G or 2G cause I have looked at those pistons you talked about. I know I don't want to go too high on the compression as i would like to go boosted. Still wondering if I go turbo or blower that I have... or both...LOL

For sure the balance shafts are coming out and the Jet Valves in the 2.0 L 4G63 head I ported.

Still trying to find someone in Ontario to regrind my cam.

Bought a timing light, I had it set to 10 Deg initial.... and 19 inches of vacuum..

At 5 Deg like the book says the vacuum drops to 15 inches.

I put it at 8 deg... and got 17 inches

This is all at idle and with the timing thing grounded.

Just for fun I checked it with the computer monitoring it... the computer bumped up to 10 to 12 degrees. It moved of course.

Is 10 deg initial too much? It didn't ping and ran pretty good. I was on 87 octane fuel also..

The thing with timing lights and setting the engine timing is there will be a variation. A belt stretched a touch, timing marks not being 100% accurate, the head milled and refaced, a worn key way in the crank... you're sort of in the dark as to what it's actually up to. I use a timing light as a diagnostic tool now. It'll tell you if the engine is doing something funky but that's about as good as it gets. It does sound like you've got it dialled in as well as can be expected. The good thing about the 4G64 is there isn't any vacuum or mechanical advance that can screw up.

8 Deg seemed ok on the drive this morning.

My plan is for a re-ring this winter if I can get my shop done.

Mopar day is next weekend so I will see if I can get into the 18's..LOL

At 2500lbs I need 150 HP to the rear wheels to run 15.00.

With my best pass, I calculated 75 HP to the rear wheels...HA HA HA I have quite a bit to go to hit 150 HP to the rear wheels. 150 hp to the rear wheels is about 190 hp at the crank... I can't see that happening without some boost.

Last tank of fuel was about 10 L/100 km.. or roughly 22 MPG

Yep, gonna need boost to make those numbers from a SOHC 4G64. The stock healthy 4G64 should make over 100 HP. If you can't make horsepower, find what is robbing it. Balance shafts are the next victim on the hit list then. Lighter flywheel, soft compound tires... anything to get it's ass off the line faster. A more aggressive cam maybe? I can't find any sources for the really cheap adjustable cam gears anymore (cheapest is a pair of Mitsubishi gears @ about $90USD)

Only a few days until I see if I can run the magical 18 second 1/4 mile.....the but dyno says it should...

BUT.. now I got a noise that sounds like a thumb from the back rocker.... weird.

Good thing I'm building this spare head.

I'm still not having any luck finding someone near me in Ontario to regrind my cam :(

there is a quick mod you can do to the ecm to make a little more power. first you need to know if you have a cal emission ecm or fed. if you take it out and pop the lid off and snap a pic of it ill point out if your ecm can have the mod.

also it costs less than 2 dollars to do and takes less than 10 minutes. these ecms come with both a federal tune and ca tune. if yours has the ca tune than you can get a little power by switching it to the fed tune.

one last thing than ill quit. if you can get a set of manual adjustable rockers from a 1984 and down mighty/ram50 2.0L, you will make a small bit of power. the adjustable rockers are more consistent than the hydro lash and dont go flat while in operation. so you get more open valve duration. this with everything done above should get you under 18sec no problem.

Yea, you should run better without the cat. Good luck on 18's.

Quote:

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Originally Posted by finalfighter

one last thing than ill quit. if you can get a set of manual adjustable rockers from a 1984 and down mighty/ram50 2.0L, you will make a small bit of power. the adjustable rockers are more consistent than the hydro lash and dont go flat while in operation. so you get more open valve duration. this with everything done above should get you under 18sec no problem.

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Not 100% sure if the mechanical rockers will like being in the hydraulically fed head. They may/may not get enough oil (could be the opposite as G63B mechanical heads were splash and splatter when it came to oiling...) but yes, mechanical lash adjusters and rocker assemblies are the way to go if you want better performance.

they work fine in the newer motors. ive been using them in my 1992 for 4 years now and have been driving the heck out of it. the only part i changed was the rockers. everything else you just leave the same. i recently did valve stem seals and the journals looked pretty much like the day i changed over to the manuals.

I'm in Canada so I'm assuming a Federal tune. I can't say for sure.

I do have a spare ECM that I need to recap and fix the lifted traces. I know the replacement had already been recapped (looked sketchy though) professionally and I had to get it from new Jersey to match the part number of the ECM that was in my truck. As far as i know my truck has had 3 ECM's due to bad caps..grrrrr

I hate having to use bodge wires to fix things, but the leaky caps wiped out a ton of the copper .. :(. I really dislike electrolytic caps in automotive uses.

Well.... I went 4 rounds and lost in the final due to a breakout...... but the truck ran 18.95 at 68mph for the runner up. Works out to about 79 HP...

Shift at 5000 in first gear and 4600 in second gear.

I almost ran the original owner of my truck in the final but he was one round shy. He has a MINT condition numbered Indy Pace Truck that used to be the Canadian Meguiar show truck.. so it's perfect.

Good job. Way to be consistent.

There is always next time...

I had them all beat on the line.. The truck just wasn't very consistent.. went from 19.17 to 18.95 throughout the day. Same shift points..etc.. grrr

Had to use the brakes on one pass as i had him so covered... imagine hitting the brakes at 65MPH against a guy to make sure I don't break out...LOL

Anyways... this brings me to another point.

On the last pass, 18.95 pass, my air fuel gauge quit (bad ground) which is hooked to my 02 sensor. I didn't think it should do this, but without a proper ground on the Gauge, the "Check Engine Light" came on. I saw the light in the staging lanes but figured out the issue after the pass.

I know the last time my truck had the check engine light on, the mixture went SUPER rich. I'm thinking the truck went faster due to the extra fuel.. make sense??? The air temp and humidity was the same all day so the density altitude did not change and the wind was consistent out of the same direction and speed.

I do know when I cruise, the engine runs in the 15.9 to 16.7 range which seems super lean, but on full throttle gets to 12.0. Maybe not fat enough on full throttle? I would think it should go into the 11's at full throttle rich.

I'm really surprised by this and it's all speculation.

Certainly the lack of a cat is worth a ton of power in this little engine. I wish I would have had a chance to finish my ported head for it.

Yep, it ran better when the engine ran rich on throttle. The fact that you are capable of breaking out of your bracket means the engine still has plenty of potential. I am not sure if the ECU in the 4G64 works this way but some OBD-II's can be forced into 'closed loop' mode by grounding the O2 wire. If it can go into closed loop you can then retune your ignition and make use of the extra fuel. It shouldn't be running that lean AFAIK so there's a chance that something is up:shrug:

Get a code reader onto it and see if there's a fault somewhere (will be hard to detect if it's intermittent) Check your plugs for visual signs of leaning out. An exhaust leak upstream from the O2 sensor? Could also be a tired fuel pump not providing full fuel pressure or a clogged fuel filter or pick up in the tank. Maybe an injector clean is in order too...

Don't forget.. this is OBD-I so I only get codes in the form of electrical pulses read on a oscilloscope or old style sweeping dial volt meter.

I'm running a fuel cell with an external electric fuel pump running at 58 psi. New lines front to back and newer filter.

I will need WAY more fuel when i go turbo.

The exhaust manifold was milled flat before installation.

BUT... I agree that I possibly forced the ECM into Open Loop for that last pass. It also pulled cleaner through the gears.

I think I'm running lean and the ECM is certainly not compensating for that.

Next year it gets a sniper system... then i will have lots of fuel..LOL

And I goofed on 2 counts - trucks are OBD-I (which you've correctly pointed out) and indeed it is open loop. There are ways to nerf the closed loop - maybe disconnect the temp sensor or grounding the O2 sensor wire:shrug:. A friend of mine was helping his former boss with his Excel Sprint Cup track car. They are forced to run stock ECU's and engine internals, but he fudged the ECU into open loop and retuned the timing. It was definitely faster on track than the other cars it was up against... I'll have to ask 'the man' ;)

http://www.mightyram50.net/vbulletin...id=25784&stc=1

huh? :scratchheadyellow: ...and here's a thought. Is ethanol in the fuel screwing with the ECU trying to maintain AFR stoic value of 14.7? It might actually be lower than that - like 14.2? And there's the mystery lean run factor. Looked at a few forums and disconnecting the temp sender seems to force the ECU into open loop (can't confirm that as fact for the Mitsubishi OBD-I ECU) This could turn into a separate tuning thread :think:

As for ethanol - I can't give this any credibility but here is something to read:

https://e360.yale.edu/features/the_c...or_environment

^
http://www.mightyram50.net/vbulletin...id=25784&stc=1

That is a good point about the Ethanol. When I go to a wide band 02 when I switch to the Sniper System in the spring I will certainly be able to check more.

I only have 1 more day of racing on October 16. I might try a few things to see if I can get some more.

I'm contemplating replacement pistons or just a hone and re-ring. It will smoke a bit N/A as I will have to open the ring gaps until I can get the rest of the turbo (or blower) combo figured out.

I'm just unsure if the Eaton blower I have can be used with a suck through as it doesn't have seals on the ends of the rotors ...

Only way to know with the block and bores is lifting the head off. If they're not carved up and there's no visible lip on the top of them, I'd be tempted to deglaze the bores and throw in some new standard size rings and call it. I don't know if the Eaton will like being set up like that. Wonder how ITB injection would go? Bike throttle bodies are hell cheap to buy...

https://www.youtube.com/watch?v=eH4QNrEZGVU

I looked at last years dial for Mopar day. I dialed 19.86.. I ran a second quicker this year with only removing the cat, change of timing.

I did fix the ground issue and my Air Fuel is fine. It cycles between 15.5 and 14.0 which is normal

Gaining a second isn't a bad effort. Column shifting is no easy feat either! Next year you'll be on sub 18 passes no problemo :thumbup:

I ran 12's in my big block aspen back in the day with a column shift... have to be precise or you go right to drive.

I think after the rebuild I should be able to run in the 17's N/A

Looked at my first pass years ago and it was a 20.33 LOL.. 1.38 sec increase in performance since then :D