How to get more torque from a 4g93 SOHC 16v (Full Version)

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How to get more torque from a 4g93 SOHC 16v

  

BobC92 -> How to get more torque from a 4g93 SOHC 16v (6/3/2005 3:07:35 AM)

Hey all, newbie to the forum here.

I have a 92 Expo LRV Sport AWD 5-speed that I picked up cheap a while back with a bad tranny. It only had 84k on it and the problem was that, in 2nd gear (only), as long as you kept your hand on the gearshift it would stay in gear just fine - but if you didn't it would jump out of gear if you let off the gas quickly. 1st-2nd syncros were also bad so it would grind if you didn't hesitate a split second in neutral during the 1st-2nd shift.

I drove it like that for about 15k miles but finally got tired of nursing the tranny along. So, I recently picked up a low-mileage replacement at one of those "engines imported from Japan" places and installed it. Now it shifts and works perfectly. I have absolutely fallen in LOVE with this little micro-van as my daily commuter - all over again!

There is only ONE thing about it that I DON'T love about it. It is in SERIOUS need of more low RPM torque. I don't like how high I have to rev it and how much I have to slip the clutch to get a smooth takeoff - especially when starting from a dead stop going uphill (a common situation here in Seattle).

I've read that advancing the cam will improve torque in the lower RPM ranges, so I'm thinking about installing an adjustable cam gear/sprocket to see if that will help. I'm also thinking about doing the IAT-resistor mod to make it run a bit richer for a bit more power. Anybody got any other suggestions?

Keep in mind that
1) I am a very capable mechanic and fabricator (I do the Jeep thing and have built all my own suspension modification and body protection parts)
2) I'm not really looking for big HP gains
3) I'm not concerned about having more top-end power either, and
4) I'm on a pretty tight budget (would I be driving a 13-year old car every day if I weren't?).

Any suggestions are welcomed.

Thanks,
Bob

  
patsevo8 -> RE: How to get more torque from a 4g93 SOHC 16v (6/3/2005 11:24:34 AM)

Boy that's a good question. I'd start with possibly airflow or like you said, advancing timing just a little bit. Not much though.

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/3/2005 6:37:47 PM)

quote:

ORIGINAL: patsevo8

Boy that's a good question. I'd start with possibly airflow or like you said, advancing timing just a little bit. Not much though.


Thanks for the reply, but I'm not really wanting to advance the timing - at least not in the traditional sense of advancing the distributor. That contributes to pinging problems and the need for higher octane fuel. Can you say S-P-E-N-D-Y?

What I'm thinking about advancing is the camshaft timing. Of course that will advance the ignition timing too, since it is driven off the camshaft, but I'm thinking I'll probably need to actually retard the timing at the distributor to compensate.

I figure if I advanced the cam say 6 degrees, for example, and the stock ignition timing is supposed to be say 4 degrees BTDC (don't know what it really is without looking it up) I'll probably have to set the timing at the distributor (or at least the reading of the timing from the crank pulley) for 2 degrees ATDC in order for the ignition spark to happen at the same point in the piston stroke. Or maybe somewhere in between 2 degrees ATDC and 2 degrees BTDC. I'll just probably have to play around with it a bit and figure out what works best by trial and error.

As for making it breathe better, I have already given that some serious thought too. Making the air flow better on the intake side always benefits both HP and torque. Things like porting heads, boring throttle bodies, swapping fuel injectors, high flow intake manifolds, free flow filters and such are all good for performance across the whole RPM range. Unfortunately though most of the benefits are gained at the high end of the RPM range - not at the low end, which is what I'm really looking for. Also there is the fact that most of those kinds of mods are anything but cheap.

On the exhaust side, making it flow too freely will actually reduce low end torque by moving the torque peak into a higher RPM range. At low RPMs torque actually benefits from some backpressure. Of course as the RPMs increase you reach a point where backpressure builds up enough to start robbing power, and at that point you need more flow capacity.

I know that there is no "magic bullet" to get what I'm after. I'm just hoping that others around here may have come up with some low-buck mods I can do that will individually make some small improvements - and just maybe collectively make enough gains to overcome the little Mitsu's one, slightly unpleasant performance characteristic.

FireDoc -> RE: How to get more torque from a 4g93 SOHC 16v (6/3/2005 7:23:43 PM)

Did you replace the japanese sensors with the ones off of the older engine? When I swapped a jap engine into my wife's little 90 eclipse 4g93 1.8L I was dissapointed until someone suggested that the sensor parameters were not the same because of the different emission restrictions programmed into the ecm. Other than that, have you thought about going irridium? NGK's are $8.00

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/3/2005 7:54:41 PM)

quote:

ORIGINAL: FireDoc

Did you replace the japanese sensors with the ones off of the older engine? When I swapped a jap engine into my wife's little 90 eclipse 4g93 1.8L I was dissapointed until someone suggested that the sensor parameters were not the same because of the different emission restrictions programmed into the ecm. Other than that, have you thought about going irridium? NGK's are $8.00


Sorry FireDoc, but I may have been a little unclear in my first post. I haven't swapped engines - only trannys. I still have my original US-spec engine.

Now that I'm back to driving it every day again, what I'm trying to figure out a way to do is to improve my low RPM torque so I don't have to rev it so high and slip the clutch so much in order to start it rolling from a dead stop.

I've been thinking about doing some minor ignition system upgrades too - they can't hurt and might even help gas mileage. I take it you like the irridium plugs. Are they that much better than Platinums? I've been thinking about getting a set of the Bosche +4 Platinums or maybe even trying some Splitfires.

Any other specific recommendations/suggestions? Better plug wires? Hotter coil maybe? Even looking for anybody to make specific recommendation of brands/part numbers of anything that has worked well for them....


FireDoc -> RE: How to get more torque from a 4g93 SOHC 16v (6/4/2005 9:37:44 AM)

My mistake on the engine bit, I assumed when you were looking for torque you had done a complete swap. As far as Iridium plugs go, they are far superior to platinum because the have much less resistance, harder metals, higher temp tolerances, etc. Here's an article that explains it. http://ducatigarage.netfirms.com/denso.html It doesn't sound like I have to explain all the benefits to you, as far as other ignition parts go you probably know all the good companies that make what you want, of course finding an application for your "Not so popular to modify" engine that isn't just going digital (as you mentioned budget) may be more difficult. I'll keep my eyes open.

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/4/2005 10:31:53 AM)

quote:

ORIGINAL: FireDoc

As far as Iridium plugs go, they are far superior to platinum because the have much less resistance, harder metals, higher temp tolerances, etc. Here's an article that explains it. http://ducatigarage.netfirms.com/denso.html



Thanks for the link - I'll check it out

quote:

ORIGINAL: FireDoc

..........as far as other ignition parts go you probably know all the good companies that make what you want, of course finding an application for your "Not so popular to modify" engine that isn't just going digital (as you mentioned budget) may be more difficult.



Yeah, that's what I'm running into all right. Not a very common vehicle or the most common engine Mitsubishi ever built. That's why I'm soliciting info from the "been there, done that" folks around here [:D]

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/4/2005 3:09:46 PM)

OK, here's an idea and a bunch of questions for all the experts out there.

I was just down at the wrecking yard looking at and comparing two wrecked Expos.

One was a 92 with a 4g93 SOHC 16v (1.8 liter) just like mine.
One was a 94 with a 4g64 SOHC 16v (2.4 liter).

I noticed that the intake plenum and throttle body on the 94 were significantly larger, but otherwise seemed to be set up EXACTLY the same. Connectors all seemed to be of the same type and size and all seemed to be located in the same places. Throttle linkages & their mounting brackets even looked interchangeable.

This gave me an idea. So, here goes with the barrage of questions.....
Does anyone know if the intake for the SOHC 4g64 will bolt onto the SOHC 4g93 head?
If not, how about the throttle body?
If it is possible to do either of these swaps, would I also need to swap the airbox so that the MAF sensor is matched to the intake?
What about the ECU? Are they mapped differently? Would it be necessary - or even possible - to swap them as well?
Or would it be easier/better to swap all my sensors & such over to the new intake & throttle body?

I'm thinking that I might be able to scrounge the parts off one of the scrap-pile engines in one of the larger yards for really cheap. On the surface, this looks like it might be a pretty easy swap. Just wondering if anyone has tried it and if so, how well it worked and what are the pitfalls. I've been calling around trying to get my hands on the intake and throttle body gaskets for both to compare them, but no one seems to have them on hand (surprise, surprise!). May have to just order them compare them and then pay the restocking fee if I decide not to acutally buy them.....

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/5/2005 1:06:13 AM)

Well, I read several posts by a number of people in various import car and "tuner" forums who vigorously maintain that modifying the IAT is pure snake oil. In one forum it was even listed in a thread called Crap that Doesn't Work - right along with fuel line magnets and the "tornado" intake inserts. SO, I read up on it some more and really got my head around exactly how the IAT mod works. I also read a few articles on aftermarket "piggyback" performance chips, and replacement programmable ECUs. From this I determined that modifying the signal from the IAT is one of the tricks that both these devices employ to enhance performance. Based on my research, I decided to go ahead with giving it a try.

Reading the IAT diagnostic procedure in my Chilton's manual told me that the IAT's resistance at an ambient air temperature of 32 degrees should be around 6000 ohms, and at 68 degrees it should be around 2700 ohms. The wiring diagram showed me which pins on the combined MAF/IAT to measure to check it, and sure enough, the resistances were right about what it said they should be. My wife thought I was nuts when she saw me putting the airbox in the freezer to get it down to 32 degrees for the test! So, at this point I had all the info I needed to proceed.

Rather than pay some eBayer $5-$40 for a five-cent resistor in the 3k-5k range and a set of instructions I decided to do it a little differently and make mine adjustable. I bought a 5k linear potentiometer, 5 foot of 18 guage speaker wire, and a 5-pack of snap together male/female "bullet" connectors at Radio Shack - all for about 6 bucks total.

I cut the wire to the IAT (red & black wire - pin 6 on the 7 pin connector to the airbox MAF sensor) and installed a male snap connector on one end and a female snap connector on the other end. I figured that, if it didn't work, I could just plug the two ends of the wire back together to UN-do the mod quick & easy. Next I threaded the speaker wire through one of the rubber grommets in the fire wall and put a male snap connector on one wire and a female snap connector on the other wire and plugged them into the ones I put on the IAT wire. Next, inside the cab, I soldered the two ends of the speaker wire to the center and end terminals of the potentiometer. VIOLA' - an adjustable IAT!

With the potentiometer turned all the way down to zero it is like nothing has been done. The ECU reads the actual resistance of the IAT. This a good thing for those of us who live in areas where passing an emissions "sniffer" test is required to renew your tabs. With the potentiometer turned all the way up, the ECU reads the combined resistance of the IAT and the 5k potentiometer - roughly 7k-8k of resistance. This translates to the ECU getting a signal telling it that the air temperature is somewhere in the 10-15 degree range.

Since colder air is denser air, the ECU adjusts the pulse width to the injectors to hold them open a tiny bit longer - to push through a little more fuel and try to maintain the correct air/fuel mixture. But, since the engine temp sensor is telling the ECU that the engine is fully warmed up, it doesn't advance the igniton timing - like it would if it were running in open-loop (warm up) mode. This is very important because one of the problems I was experiencing was knocking and pinging when engine was pulling hard at low RPM with the throttle wide open (a.k.a. "lugged down"). When taking off from a dead stop - especially uphill. I was having to rev the engine up into the 2000 RPM range (that's just an estimate - since it doesn't have a tach) and then slip the clutch to avoid "lugging" the engine and having it ping and lurch etc.

I took it for a test drive and the difference/improvement was quite obvious. IT WORKS! Not what I'd call a dramatic improvement, but definitely noticeable. I went over to the parking lot at my son's school to do a little low-speed testing. The lot is set up with two parallel parking lanes about 100 yards long with a row of parking stops in between, and it is on a slight hill. I did about a dozen "laps" around the row of parking stops in 2nd gear to test it at various settings of the potentiometer. Everytime I came around the end of the row I let it slow all the way down to just under 10 mph, and then as I started the uphill run I'd floor it. With the potentiometer set to zero the car would lurch and ping very badly and barely manage to accelerate to 12 or 13 mph by the end of the row. With the potentiometer set to the middle setting (~ 2500 ohms) it was a little better, and with the potentiometer turned all the way up to 5000 ohms it was MUCH better. Barely pinged or lurched at all and it accelerated to 15 mph!

Next I drove it around the neighborhood doing multiple starts from dead stopped with various potentiometer settings. My "seat of the pants tachometer" tells me that if it takes 2000 RPMs to get a smooth startup with the dial set to zero, then it probably only takes 1500 RPMs to get a smooth startup with the dial set to 5000 ohms. That's a BIG improvement. I'll probably hook up a tach to test it and get some actual numbers, but there is no question, based on the old "butt dyno" that there is a definite improvement.

As my last test I decided to do a high-speed hill climb. We live on top of a hill that is about 600 ft high, and one route to the top is a 3/4 mile long, divided, 4-lane street, that is a 6% grade. I hit it in 3rd gear at 40 mph with my foot on the floor and the dial set to the 5000 ohm position. Initially I was accelerating up the hill, but as it got steeper it stabilized at around 50 mph as it got into the long steepest section in the middle (50 mph is the speed limit on that road BTW). After a couple of seconds I spun the dial to the zero ohm setting to see what would happen. The engine almost instantly started to ping and ever-so-slowly loose speed. After a few seconds I then spun the dial back to the 5000 ohm position and, just as quickly, it STOPPED pinging and started slowly regaining the speed it had lost! Heck, for my money, that would be worth the 6 bucks and 3 hours invested (including tracing the wiring, testing the IAT, and the trip to Radio Shack) right there!

So, now the only thing that remains to be seen is the mod's effect on gas mileage. The eBayers claim up to a 20 HP gain and equal or better mpg from this mod. Now, I know that the boost is less than that - 20 HP added to an engine that only has 112 HP to start with would be a MUCH more dramatic-feeling improvement. However, I'd be willing to believe that it is somewhere close to 10 HP, give or take a pony or two. If that means I don't have to floor it quite so often, then just maybe the mileage won't be negatively impacted - or at least not much. Of course, I do have the option of turning the mod off every time I get on the freeway if I like, so maybe I can just get in the habit of turning it on and off depending on how and where I'm driving. Or maybe setting the dial at the halfway point to get a balance between the max power boost and max fuel economy will be the answer. Who, knows? We'll just have to see how it goes.

I'm still looking for other suggestions, looking for an adjustable cam gear, and wondering about the manifold & throttle body swap though. So, if you're reading this little book I've written, and have some more suggestions for cheap mods, or info about the intake swap idea, then bring 'em on! I'm not satified just yet - but I wanted to share what I did and what the results were with anyone who might be interested.

BobC92 -> RE: How to get more torque from a 4g93 SOHC 16v (6/5/2005 10:30:39 PM)

WOW! I can't believe that there isn't more activity around here. From what I've read, the 1.8 liter and 2.4 liter engines in the Expos are the same ones that were installed in Mirages, Lancers, and Diamantes. I would have expected the resident experts to be coming out of the woodwork around here by now. Instead I kinda feel like I'm talking to myself......

Oh well, here goes anyway. FWIW I took it one step further today. I went back to Radio Shack and picked up a 10k ohm potentiometer, a knob to fit on the shaft of the potentiometer, and a small project box.

I replaced the 5k ohm pot with the 10k ohm pot and put it inside the project box. The box is just the right size to wedge into the open space right under the stereo (where the factory equalizer would go - if I had one). Then I put the knob on it and wedged it into place. VIOLA', now my adjustable IAT is complete, easy to use, and even looks nice!

I fiddled around with it a little and it seemed to work best with the potentiometer set to around the 2/3 to 3/4 mark - around 7k ohms. Combining that with the approximately 3k ohms from the IAT (at about 65 degrees) it is basically telling the ECU that the ambient air temperature is around 15 degrees below zero Farnehiet. [;)] Cranking it all the way up to 10k ohms for the ECU to get a signal totaling around 13k ohms (again, at 65 degrees) would be telling the ECU that it is -50 degrees outside. That might be a little too much - but we'll see. I plan on drving it for a week at the 1/4 setting, then for a second week at the 1/2 setting, and a third week at the 3/4 setting, and finishing up with a week at the max setting. That way I can compare gas mileage, driveability, etc. to see what works best.

I think I've taken this mod about a far as I can go with it, now it is just a matter of fine tuning it to see what setting works best. FWIW, I went ahead and ordered the intake and throttle body gaskets for both the 1.8 liter 16V SOHC engine and the 2.4 liter 16V SOHC engine at the local auto parts store. When they come in I'll probably buy them both, take a few days to compare them, and then maybe return one or the other for a refund. That ought to tell me if the intake and or throttle body transplant would be a direct bolt on or not. I'll report what I find out after they come in later this week.

Don't know if there is anyone even reading this, but if so, I hope someone sometime will find it helpful. I'll continue to report results if there seems to be any interest.........

  

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