Srt-4 VS 05 Evo

[Igovert500]

Originally Posted by chexmixa

with higher octane my Boost doesn't drop off as much at higher rpms so essentially thats a 5-10 hp gain. I even stated that it was a gain at higher rpms. If you check out a dyno of an Srt-4 you will see his HP drop dramatically past 5500 rpms. With higher octane you don't drop as hard. you fall to 14 pounds of boost rather then 12-13.

I really think you are misinformed on this. Typically, stock turbos don't hold the boost to redline..because they are smaller sized turbos designed to give good power in the low and medium rpms. Huge turbos have longer lag, because it takes longer for them to reach full boost, but they can hold that boost through redline.

Yours maybe like mine, they aren't capable of holding the peak stock levels to redline. Mine are set at 12 stock but start falling after 5000rpms and only can hold 10psi to redline. Simply the turbos aren't very effiecient at higher rpms. A freer flowing exhaust and intake will allow you to flow a more, but adding higher octane fuel doesn't automatically do it.

The only way what you are describing is possible is if on 93 you are getting knock in the higher rpms, and the ecu is retarding timing (lowering hp)...and when you put in 100octane no knock is detected so the you can run at full power. But simply adding higher octane without changing the boost levels doesn't add hp at any rpm, unless your ECU is already pulling timing.

So basically, either your turbos can't flow that much to redline (in this case, higher octane fuel alone wouldn't change anything at high rpm levels, without other modifications)

Or stock your ECU has to pull timing or opens the wastegates early because it is detecting knock or you are approaching fuel cut. And higher octane fuel alone retards the knock and allows you the full power.
Otherwise I don't see how higher octane alone makes you hold more to redline without modification. If you are stock, I simply don't get it.

If I'm incorrect, please find me something to read, because I just don't understand it.

[chexmixa]

To be honest i'm not sure how it works. But depending on the type of fuel i use determines my boost. For example. I filled up with shell one time with my car and noticed i could not reach full boost using their gas. After then tank i filled up with race gas and was holding full boost for longer and spikeing up to 17, i would only drop down to 14 psi at red line. I believe we even have the same turbos, your 2 to my 1. So i don't know exactly why it does it.

[Igovert500]

We definantly don't have the same turbos, I forget what your car utilizes (it's been awhile since I read up on it) but in mine are TD04-9bs and I know your's has a larger compressor wheel and I believe I read it spins in the opposite direction. So suffice to say, they are not the same. However, that wasn't the point.

Here Neutrino essentially says the same thing I was trying to say:

"while higher octane in itself will not increase power. higher octane gas will allow the ECU to run more agressive timing and closer to the max power 14.40 A/F (.98 lambda) ratio since it doesn't have to worry about knock so much.

So yes higher octane gass will allow the ECU to give you more power. Therfore there will be a performance increase. That is up to a point though, since most ECUs are not programmed to take advantage of ultra high octane racing fuels and such."

Taken from:
http://www.automotiveforums.com/vbul...=higher+octane

Basically, my point is, yes you can run more boost with higher octane, but I don't see your ECU uping the boost on its own when you run race gas. So...I'm skeptical.

[Drifty]

Please continue i am learning and i did reaserch the turbo on an srt is a Mitsubishi TD04-L-16GK

[Igovert500]

Well there you go. Same housing, different compressor wheel. As far as the original disagreement, I've been doing some searching, and all I keep finding is "maximum boost — between 11 and 14 psi, depending on conditions"

Obviously, that doesn't explain a whole hell of alot, but some more comments:

1) You say your boost spikes to 17psi, and then falls to 14 on 100 octane, 12-13 on normal premium gas. Many turbos spike, that isn't necessarily a good thing, and a spike indicates a short one second spike...not that you continually are boosting 17psi, so care to explain what you boost levels are all the way through the rpms on both octanes?
All that I have read says 14psi tops, I'm guessing the ECU accounts for atmospheric conditions and if it detects knock it brings it back down to 11-13psi. 100 octane would reduce that problem allowing 14psi to redline. So we were both right in that respect, if this is the case.

However, just to clear up one thing. You said you do in fact gain hp due to those few extra psi. While this is true in a sense, you don't gain peak hp...it stays the same, as you are peaking at 14psi in the midrange rpms. You are talking about more hp closer to redline. So this doesn't add to your peak hp, but does in fact help your powerband. So if I am interpreting this all correctly, we were both right in a sense.

If you can find further info on this subject specific to srt4s, I would be interested in reading it. As I read somewhere that in '04 or '05 they swapped in larger injectors??? Just wondering if this is to please the aftermarket enthusiasts, or to compensate for the fact that they get knock at stock boost levels sometimes. So yeah, if you have any info, let me know.

[Sleepr awd]

Originally Posted by Igovert500

1) The stock evo runs 20psi??? Are you sure on that one?

i do believe i read somewhere that the EVO stock runs 19psi, not entirely sure i remember where i read it, but i did!!

[chexmixa]

Originally Posted by Igovert500

Well there you go. Same housing, different compressor wheel. As far as the original disagreement, I've been doing some searching, and all I keep finding is "maximum boost — between 11 and 14 psi, depending on conditions"

Obviously, that doesn't explain a whole hell of alot, but some more comments:

1) You say your boost spikes to 17psi, and then falls to 14 on 100 octane, 12-13 on normal premium gas. Many turbos spike, that isn't necessarily a good thing, and a spike indicates a short one second spike...not that you continually are boosting 17psi, so care to explain what you boost levels are all the way through the rpms on both octanes?
All that I have read says 14psi tops, I'm guessing the ECU accounts for atmospheric conditions and if it detects knock it brings it back down to 11-13psi. 100 octane would reduce that problem allowing 14psi to redline. So we were both right in that respect, if this is the case.

However, just to clear up one thing. You said you do in fact gain hp due to those few extra psi. While this is true in a sense, you don't gain peak hp...it stays the same, as you are peaking at 14psi in the midrange rpms. You are talking about more hp closer to redline. So this doesn't add to your peak hp, but does in fact help your powerband. So if I am interpreting this all correctly, we were both right in a sense.

If you can find further info on this subject specific to srt4s, I would be interested in reading it. As I read somewhere that in '04 or '05 they swapped in larger injectors??? Just wondering if this is to please the aftermarket enthusiasts, or to compensate for the fact that they get knock at stock boost levels sometimes. So yeah, if you have any info, let me know.

What i ment by the gain in horse power is in higher Rpms. I don't gain any peak HP at all. The higher octane cause my boost not to fall off so dramatically.

The 04-05 Srt-4's have bigger fuel injectors and LSD. They are 477 (forgot the unit you put after that) They are the same injectors as the stage 1 upgrade for the Srt-4. The 04-05 have 15 more hp and 10 more lb/tq due to the injecters and an updated ECU.

The reason i figured we had similar turbos is cause mistu makes mine. It is the same turbo as the Evo except slightly smaller and doesn't have the duel spinning compresser wheels. Most Srt-4s boost 15 psi stock and have a 16-17 psi spike from 4k rpms to 5krpms. At 5.5k without Software upgrades + wastegate your boost starts to fall off. Off the top of my head i wouldn't know where to look for this info.

www.SRTforums.com is a great site to find information on the Srt-4. The forums there are loaded with info. Just be carefull with the war stories section as lots of the Srt-4 owners think thier car is unbeatable. You can easilly get yourself dragged into an arguement there.

Edit: where is Stiener when you need him? he could easily clear all this up about the evo and the Srt-4 considering he used to have an Srt-4 and ownz an Evo. I was talking to a few people last Sat about their Evo's at a local car meet (Pavilions in scottsdale) they were reporting stock boost to be at 20-22 PSI for 03-05 Evo XIII. I am not lieing or embellishing anything there is nothing for me to gain. I don't know the boost levels on the Evo for sure. I am just reporting what the EVO owners i was hanging with told me.

[Igovert500]

It's cool, I just never realized they boosted that high stock, wasn't calling BS, just wan?ed to clarify. You learn something new everyday right...

[chexmixa]

Originally Posted by Igovert500

It's cool, I just never realized they boosted that high stock, wasn't calling BS, just wan?ed to clarify. You learn something new everyday right...

Yeah when i first heard it too i wanted to call BS. But then i started to think about it. a low compression 2.0L without variable valve timing with 275 hp to the crank? Def gotta be high boost. I guess their turbos have 2 compresser fans that run opposite ways from each other or something like that. their turbos are also only good for 25psi so their just about maxxed out.

[2of9]

Yeah, i heard the new Evos were coming with the MIVEC engine thingy too. Well, we'll just have to see if Mitsu succeeds with it. Nice race thought anyways. As a DSM person, I havent heard of the Evo 8s runnin 20 psi stock, but i have heard that they do boost around that much stock.