93 Legacy Sport Sedan engine management questions

[BoneIslandScooby]

Do the Turbo Legacies run batch fuel injection or sequential fuel injection from the factory? Does anybody have any experience tuning these cars for better fuel economy? If so, how did you do it? If they run batch fuel injection, I imagine converting to sequential would help. Of course, that would require switching to a standalone computer if it doesn't come with sequential fuel injection from the factory. Any info or suggestions? I also want more power, but looking to run more than one map. Want at least one map for daily driving, and one for autocross events / performance.

[BoneIslandScooby]

According to Wikipedia, "When it debuted in the US, it was introduced with a slightly larger displacing SOHC 2.2-liter 135 bhp (101 kW; 137 PS) engine that was also used for the European, British and Australian versions over the Japanese market version of DOHC 2.0 liters. The 2.0-liter and 2.2-liter engines fuel delivery were managed with sequential multiport common rail fuel injection called MPFI....". Of course, in this passage, as evidenced by the horsepower level quoted, they are specifically referring to the NA version. I seriously doubt they'd downgrade the fuel injection on the turbo model. So fuel economy and power gains cannot be made by switching to sequential fuel injection by installing a standalone. Could the improvements I want to make theoretically be possible with a piggyback like the PP6 or PP8 as well as with a standalone? I know Legacy777's opinion about going the standalone route. I would like to hear more about the technical reasons why a piggyback won't work for my purposes.

[Legacy777]

As you discovered, yes these cars use sequential fuel injection.

The fuel economy is not great, and one of the reasons is because they do not have an intercooler, so extra fuel is used while under to boost to keep combustion temperatures in check. The main issue with piggy backs is that they work by "fooling" the ECU, however over time the ECU will tend to learn around the piggy back or may not produce consistent results.

Are you looking for better fuel mileage under cruise conditions or just normal driving mixed boost & non-boost. Best way to improve your fuel economy is to stay out of boost. Besides that, any turbocharged engine is going to drink, not sip fuel while in boost.

With my stand alone I can get pretty decent mileage when cruising on the freeway and if I stay out of boost, but if I'm heavy on the accelerator and am in boost a lot, then my mileage goes to shit. That's just the nature of a turbocharged engine.

[BoneIslandScooby]

Yeah was hoping to keep the engine out of boost for normal daily driving to get max economy, and get max performance for events. Wanted to achieve this by running a couple of different maps. I was even hoping to be able to run 87 octane for daily driving for an additional savings in fuel cost. I think I might go with microsquirt, because I have a guy locally who has tuned his own turbo converted vehicle with the megasquirt, and he also competes in the events that I hope to participate in.

[BoneIslandScooby]

Josh, and anybody else who might want to chime in... What if I used a Rob Tune computer for a baseline tune, then used a piggy back on top of that for the alternate fuel and ignition maps? The alternate maps would be for an occasional run at the drags and for max fuel economy. Either way, I wouldn't care about mid-range power or how smooth the power delivery is because at the drags all you are looking for is full throttle power. For max fuel economy, all I care about is using as little fuel as possible, and using the cheapest gas possible. I would dial out boost, tailor back the fuel, and dial some spark advance back in. I'm looking for a way to have an easy and inexpensive upgrade path, while still allowing for some way to run a different tune. I know I can somewhat achieve this with an electronic boost control, but that wouldn't do anything to the fuel and ignition, except what the factory computer already does in response to changes in boost, RPM, throttle position, a/f readings, etc. Might the EBC be enough to achieve what I want?

[wtdash]

HI,
If you stay out of boost, you'll get close to 30MPG highway w/the Rob Tune, from what I've read on here (I have it but no road trips yet to verify). And you'll still get a BIG increase in Hp/Ft-lbs. I know you're wanting to make this harder than that ( ), but you might just get the best of both worlds w/a Rob Tune.....My car did great @ my last AutoX w/the Rob Tune....my driving skilz? Not so much (yet).

You'd have to run 91/92 all the time, though.

Also, a piggyback on top of the Rob Tune wouldn't work (well), as the stock JECS MAF (required w/EJ20G ECUs) is about maxed out w/the 525cc's and a TD05-16G/VF39. I guess you could use it for economy, but I think your cost/benefit is starting to become a concern.

GL,

TD

[BoneIslandScooby]

The cost concern is about spreading the cost out little by little, from mod to mod. There's no doing that with a standalone computer. It's a big investment in parts and labor (unless you do it all yourself) right out of the box. I can do intake, then exhaust, then intercooler, then boost control, then injectors, then turbo, then AWIC, then piggy back, then methanol and/or extra fuel injector. You probably are right that I might get as good fuel economy as I could reasonably expect out of the Legacy with the Rob Tune. I also get the feeling that I would have as much power as I'd ever really want or need with the Rob Tune. But then, truth be told, I would still want to see what could possibly be done in the way of a tune to max out fuel economy, and possibly allow for the use of regular from time to time. I wonder if anybody has ever done this.

[wtdash]

On here? I'm not sure, but you could talk to Hyundai :

Veloster Turbo (twin scroll turbo), full boost @ 1750 RPM, 38 MPG highway, makes 200HP from a 1.6 4-cylinder DI, 9.5 CR, max of 18 psi on REGULAR petrol.

Td

[James614]

Direct injection has properties you simply cant achieve by tuning. If you want that kind of blend of performance and economy on regular fuel from these engines you're talking engineering your own fuel system and re-shaping the combustion chambers at the least.

On these engines (and most other port fuel injected forced-induction gasoline engines) you will likely have to sacrifice MPGs to run regular, unless you managed to limit boost to just a few PSI or less.

[BoneIslandScooby]

Limiting boost is at least part of the plan. Closely monitoring A/F ratio, and dialing some spark advance back in is also part of it, though how much advance I can add back in is obviously limited by lower octane. Maybe water / methanol injection is part of the answer as well? I like the system MRT has on their site. The cool part is it runs on it's own without needing a piggy back or standalone computer to run it. In other words, it seems to work with the factory engine management computer.

[wtdash]

Maybe water / methanol injection is part of the answer as well?

Read posts on here from Skid542 as he ran/runs this on his car. He didn't want to go w/an intercooler so did methanol (?) injection to lower intake temps. He doesn't post on here much anymore, but you may be able to PM him if you have questions.

Td

[BoneIslandScooby]

Thank you for the heads up.

[BoneIslandScooby]

Has anybody ever used the Apexi Power FC for 92-96 WRX's? If EJ20G ECU's work with our cars, why wouldn't this Standalone, which was made to replace the EJ20G ECU, also work for our cars? I understand tuning might be clunky, but it is, in fact, tunable. It supposedly comes with base tunes based on the factory ECU's being replaced. I wonder what Rob could come up with if he got one of these in his hands.

[James614]

I believe at least one on here is running it, and a few have looked into it. You'd have to search for the posts... It would be backwards for Rob to tune it, since he can tune the stock ECU its a waste of $1000 to do the same on a PFC.

[BoneIslandScooby]

I discovered that a guy named Doug at Top Speed Motorsports in Alpharetta, Georgia is apparently very good at tuning the Power FC. That's close enough to me. I'd make that trip to get a rock solid pro tune that's fully optimized for my setup. I'm not sure how it works with running different maps, but I've fired off the question, and I'm going to see what they answer back.

[macipusy]

I have found that the best way to increase MPG is to up the size of the turbo, and then tune. The reason being, the vf11 spools like at 2200 RPM, so it seems like you are always in boost on the highway or really anywhere above really light load....eating mad fuel.

When I jumped to a vf39, is where I saw a huge increase in MPG. The full boost is around 3500 RPM and much easier to stay out of it if you want fuel economy. I tripled the power while doubling the MPG. On E85, I get better MPG then I did in stock mode.

[BoneIslandScooby]

VF34 will be about the same if not better than that correct? VF30 and VF34 have same compressor and the same exhaust housing. The VF34 spools up to 500 RPM quicker than the VF30 due to the ball bearing design. Would you say that the VF39 is similar in spool characteristics to the VF34? BTW, how do you manage to run E85? How are you tuned?

[macipusy]

I think the larger vf series turbos are similar in max power output with small variations. Quicker spool is nice, but not crazy like the tiny vf11. Staying out of boost to conserve gas should still be no problem at all on the vf34.

I am running the Haltech Sprint 500 standalone and do all tuning myself. I rent dyno time by the hour from my buddy Harvey at the Boostcreep. I usually do fine tuning on the street. Ive been running on E85 for 3.5 years now and can't wait to do the same to my TW.

Stock ECU sucks, IMHO, and any piggy back system basically polishes the turd that the ECU is.

I have heard good things about Rob tune, I just don't know how flexible it is if you change up power modifications or if it can do E85 tune.

[BoneIslandScooby]

It's basically an OTS tune, though a good one at that. If you use the list of equipment that he specifies, according to all the info I've read from people who have experience with it, it works quite well. It is currently limited by the MAF, which is a JECS green label MAF. Any turbo which would put the Air Flow out of the range covered by that MAF will not allow additional fueling to take advantage of the additional airflow, and would therefore cause the engine to run lean. As long as the boost control is set so that the turbo does not flow too much, then it is safe.

How many miles on your engine currently? What kind of miles per gallon do you get with your E85 tune? I see your lower end is far from stock, however, so I'll bet you can handle a bunch more power than I could with a 119,000 mile stocker. (or am I mistaken?)

[macipusy]

Actually the 91 Turbo Legacy has a stock bottom top and end with 275,000 miles on the clock. The built motor is going into my Impreza RS. It's pushing 250awhp/300awtq at the moment at 16psi on vf39.

The biggest benefit I found, by going to standalone ECU, is running speed density vs MAF. The car just runs superb as compared to the MAF setup.

I am getting about 200 miles to the tank on E85. When car was stock with vf11 and tiny injectors, I was only getting 180 miles to a tank on 91 octane. So, with 30%+ added fuel, I'm still getting better mpg then stock, on E85. On 91 octane, I get 300-350 miles per tank, but I usually stay out of boost on pump gas and the tune map is slightly richer for safety.

[BoneIslandScooby]

So, almost double the mileage on pump gas comparing stock on pump gas to current setup. A better than 10% increase in mileage on E85 as opposed to stock running pump gas.

[Legacy777]

So, almost double the mileage on pump gas comparing stock on pump gas to current setup. A better than 10% increase in mileage on E85 as opposed to stock running pump gas.

These numbers are going to vary, so just be aware of that if you were wanting to do the same thing. Mileage is going to be heavily dependent on the tune, and there are some things you can do with a stand alone to improve mileage where you wouldn't be able to do with the stock or mass produced ECU/tune.

[BoneIslandScooby]

Just spoke with somebody at Top Speed Motorsports in Alpharetta Georgia. They are known to tune the A'pexi Power FC. Apparently, since the part of the fuel map that would most affect fuel economy would be in a different area than the part of the fuel map that would affect peak power, a tune for fuel economy and power are not mutually exclusive. I hadn't thought of it that way before. Obviously, you want to increase efficiency over the whole power band, which already has a positive effect on fuel economy, but I'm sure a little bit of optimization can be done in the lower revs for fuel economy. It's just a matter of disciplining your right foot in order to stay out of boost. Now, running 87 octane would surely require a completely different tune, along with turning the boost controller all the way down. Now, can a boost controller limit boost even below wastegate pressure if need be?

[BoneIslandScooby]

All that said, I don't want a peaky tune either. I would like power to come on gradually starting at 3000 or so. You can stay below that in traffic if you mind your foot. As soon as I floor it out of a corner, I should be in the power band. Sound about right to everybody?

[free5ty1e]

Now, can a boost controller limit boost even below wastegate pressure if need be?

Nope. Wastegate pressure will always be your minimum boost level.

You can change wastegate actuators to achieve a different minimum boost, though.

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