Turbo losing power after warmup

I recently got a 2003 EVO, my 1st turbocharged car. I like the car a lot, but it seems to lose a fair amount of zip after initial engine warm up. This is just by the seat of the pants, it's still fast, but SEEMS a little less so, especially in the lower revs. I understand turbos are especially susceptible to atmospheric conditions & temperature, and as with normally aspirated cars I have owned it seems to run better some days than others. Maybe this power loss on warm up is an aspect of this? Also, exactly WHAT atmospheric conditions lead to a decrease (or conversely, an INCREASE) in power? I understand ambient temperature is one, although living in Ohio where at the moment it is 30 degrees, I don't really note (again, seat of the pants) any INCREASE in power over, so 70-80 degrees. What about barometric pressure? Seems like the denser air of a higher barometer day would produce more ponies. How about humidity?

TIA

Dan

Reply to
Dan
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I don't know much about the EVO turbo, although I know a bit about turbo's. That said, does it have an intercooler ? Does it get adequate air ? A turbo without an effective intercooler would lose power after warmup since a hot charge is much less dense than a cool charge. With a turbo, cooling the (hot) charge is very important.

A turbo will generate much more power with cool conditions (say 30F) then it will at hooter temps (70F). Most drivers _do_ feel a difference.

You usually feel it the other way. The first day temps climb above

70 degrees you will notice a reduction in power.

I don't know enough about barometric pressure to answer this question properly. I do know that turbo's will lose power in the mountains, as any car will. A turbo run by a computer (most today) is much better at compensating for it than a NA car.

However, I've never noted any of my turbo friends or my own car responding differently due to barometric pressure on a day to day basis.

Generally humidity is good for an engine. In fact, some highly boosted applications use water injection as a necessary feature. Again though, I don't think I've seen any reports of day to day differences in driveability due to humidity (on a turbo).

Reply to
Jimmy

Jimmy-Thanks for the reply. The car does have a large intercooler, as well as a sprayer to cool it evaporatively. It's a pretty advanced setup. Again, the apparent loss is minimal and quite subjective, being "seat of the pants", mostly that initial satisfying push that comes at the lower end of the turbo's range. In my fairly limited experience driving the car in the cold (30 degrees or so) I can't really say it feels "uniformly" quicker than say 50-70. I did notice on particularly hot days this past summer (got the car on memorial day) 80-90 seems to sap it a bit, as would be expected. But again these are merely impressions & not quantified in any way. I think I'll get an aftermarket boost gauge so I can at least monitor that aspect, give me something else to obsess over ;-)

Dan

Reply to
Dan

It may be that your intercooler is good enough to keep up at mid range temps and not lose power. However, you really should feel a difference down around 30 and below.

Most of us use the "seat of the pants" or "butt dyno" for rough testing. :-)

A boost gauge may or may not show you anything of interest. If the car has none, it's a nice add-on. It will also help you determine when the boost levels drop due to a mechanical problem (sprung a hose leak, sensor issue, whatever).

However, it will not show you much concerning air temps and boost. The reason is that the actual amount of boost the turbo is allowed to provide is capped at a fixed limit. You car will provide that maximum boost when you open the throttle wide, along with maximum fuel, subject to limitations such as knocking. Should there be an "issue", the computer will reduce boost to correct the problem. When the temps are low, you car may be able to generate more power while still not exceeding the maximum boost (cooler air, denser charge, more power). In fact, your car will never exceed the maximum allowable boost, since the computer will adjust to compensate. What that means is that you will probably see maximum boost in both hot and cool weather, although you may get more power in cool weather.

As an interesting side issue, you might play around with high octane gas that they sell at places like Sunoco and see what you think. Turbo's will knock with lower octane due to the effective increase in compression and the computer will reduce boost to compensate. With high octane gas, you give the computer more leeway to provide extra boost. It may not be worth the money to use it on a regular basis but Premium is a definitely good idea in most turbo's.

Now, all that said, you should probably check out one of the Mitsu groups or BBS's for more specific info. Each turbo is a little different in implementation and there are tweaks and specifics that I don't have a clue about. You could try alt.autos.mitsubishi. Also, you might want to post at

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. I don'tthink your car is a DSM but they should have a pointer to some sitesfor your particular car.

Reply to
Jimmy

I had an old 1984 Dodge 600ES, which had a turbocharged, multipoint fuel- injected 2.2l I4. Lacking a boost guage, the overboost limiter was a combined system of hardware, software, and wetware. Without a direct linkage to the wastegate, the engine control unit would indicate an overboost by turning on the POWER LOSS lamp. If you did not back off the throttle, it would eventually cut the fuel injector pulses to prevent engine damage.

In my car, the delay was about zero. The engine went from max power to engine braking with such violence that the front engine mount snapped off, and it took me several minutes to realize, as I coasted to the shoulder, that the engine was idling just fine. Reading the owners' manual helped me realize that what happened was almost normal (the broken mount was discovered by my mechanic, later).

Reply to
Richard Bell

Jimmy-Yeah, I am running the 94 octane from Sunoco. At the moment, it's not toooo bad here in central Ohio, about $1.69. On the boost question, this particular setup goes pretty high, 19 lbs, that's mainly how they get 271 HP out of 2 liters. I'd just like to monitor it as much out of curiosity as anything. There is a web discussion site on the EVO, but there's a lot of nonsense on there. Not only off topic junk, but people posting a lot of unsubstantiated crap about the car, aftermarket parts, etc. It can be a good source of info, but it takes a WHOLE LOT of SIFTING ;-) BTW I think technically the EVO isn't considered a DSM car, though I am gong to check out that site.

Thanks again for your input.

Dan

Reply to
Dan

Richard-This car has a rev limiter which has surprised me by backing off on the thrust a couple times when I got to the 7,000 redline, but it's not really violent. The car really is still pulling nicely at that RPM, some aftermarket tuners offer reflashed ecu's which will allow the motor to rev a bit higher to spread the power band a tad. One sudden shock I had during acceleration came after I had removed the intake plumbing to install a cruise control & subsequently hammered it out in the middle of nowhere. There was a very loud pop, followed by loss of power & the car refusing to run at over 5 mph, as I limped to the side of the road. Turned out I hadn't tightened the hose from the intercooler to the throttle body sufficiently, and the turbo pressure blew it off. Since the MAF sensor was no longer in the intake path with this hose connected, the car wouldn't run much about a sloppy idle. Took the computer some miles to sort it all out even after I reconnected the hose.

Dan

Reply to
Dan

Around the NorthEast, "super" is usually 93 octane. Works well and is cheaper than Sunoco. But, Sunoco will also sell you higher octane ratings last I checked (if you are willing to pay).

That is an awful lot of boost for a stock car. The HP sounds about right. I know guys pulling about 300HP from 2.0 liter Saab turbos with around 21/22 lbs of boost so you're in the range. You must get some nice mid range torque. I hope the beefed up that motor a bit for that 19lbs. Most guys do some serious building out when they get into those numbers.

I'm amazed that they'd build a car with that kind of boost and no boost gauge. Do a bit of reading before you install one. There are often different places to tap and read slightly different things.

Too bad. The DSM sites tend to be pretty good... at least last I checked. A lot depends on who moderates and runs the board. Ask about other boards, see what you can find.

Reply to
Jimmy

I agree the omission of a boost gauge in a car of this type is fairly glaring. Mitsu does make a "sport meter kit" accessory which includes a boost gauge, oil temp gauge (also good on a turbo) & voltmeter (fairly useless). It's $464! No thanks. I have heard that electronic boost gauges are superior to the mechanical variety, and I've heard the opposite as well. I do understand the difference in method of operation (remote sending unit as opposed to a tube running to the dashboard). I'm wondering if anyone here has had an particular experience with aftermarket boost gauges & can make any suggestions as to make, design, etc. I would prefer a smallish analog gauge. If nothing else running a wire should be a bit more straightforward than running a tube, I imagine either's pretty easy though.

I don't think engine durability will be too much of a problem. In the rest of the world this car is actually called the "Evo 8", because they've made seven previous versions over the past decade or so. This is the 1st to be sold in the US. Plus it's basically their rally car (competes against the Subaru WRX) & gets quite a beating in competition to help sort out the bugs.

Dan

BTW Sunoco 94 was $1.59 yesterday! Almost low enough to make me not wince so much over the 18-19 mpgs!

Reply to
Dan

Their "rally car" costs about 20 times more.

Reply to
alan

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