SRT-4 upgrades

[ScottD]

My SRT-4 has the following mods:

- Stage 2 w/out toys
- Mopar cat-back exhaust
- Mopar short throw shifter
- Motor mount inserts
- K&N drop in
- Toyota Supra PCV valve

I'm strongly considering a DSP and a wideband in the future.

Beyond that, what other mods make sense? Some items I'm considering are:

- AGP direct fit intercooler (I do not want to modify the front fascia, etc.)

- Walbro 255 fuel pump (seems to be a lot of discussion on SRT forums about fuel pump re-wire which may in fact be weak pumps)

- Forward Motion E1 Enforcer turbo

My goals are pretty modest, I just want to maximize the stage 2 that's on there. Thoughts/opinions appreciated.

[contraption22]

First things would be the DSP. You'll love it. I liked mine, but took it out because i do not yet have a wideband and fear leaning out.

Then before you upgrade anything else, I would get the 255 pump, and a wideband.

I have the E1 turbo turbo, and really like it. I didn't gain any power from it without the DSP, but I do like the increaded drivability. Once you can tune with the DSP, you will see gains overstock with an upgraded turbo.

Then I would do the intercooler.

From what I have read, the above, with slicks, should give you a low 12second car.

[ScottD]

Thanks Mike. Did you think the 93 tune on the DSP was too aggressive? Or did you just not want to tune without the wideband?

I definitely do not want to tune with the DSP without a wideband on there.

[contraption22]

I am just afraid that the DSP tune won't have enough fuel for my car with the E1 I have on it. It might, but it might not. I won't know till i get a wideband on it.

[Mopar318]

I would go for a larger than stock downpipe as well. Stock one is pretty small at 2.25".

I hope to go 11's on stock turbo with a DSP, Full 3", better intercooler, and slicks. I went 13.9 with the bone stock srt setup and open diff, which was quicker than all the stock srt's at the track that night. I think it may be doable.

[contraption22]

Also Scott... while this is not a performance mod per say, you will want to get an oil seperator in between your PCV valve and intake manifold. When you take your intercooler off, you'll see why :).

[Keito]

I've been running the 93 tune on my car most of the summer.
I can tell you with my mods, I'm hitting the COT, wideband goes in the 10's at WOT.
I need to have duster360 turn that off so I can tune.
On my car the 93 tune was weak compared to my Stage 2 W/toys using a Kinetics
wastegate actuator.
I was only boosting 15 lbs with the tune.
I turned up the boost 10% and I'm hitting 20 now.
Added a little fuel and I'm close to keeping it out of COT
Mods are: Stage 2 W\Toys, DCR T body, 3" catless downpipe,(Stock exhaust) ported E mani, big wheel stock turbo, DSP 93 tune.
I have a computer to datalog, just need to do it.

[contraption22]

I've been running the 93 tune on my car most of the summer.
I can tell you with my mods, I'm hitting the COT, wideband goes in the 10's at WOT.
I need to have duster360 turn that off so I can tune.
On my car the 93 tune was weak compared to my Stage 2 W/toys using a Kinetics
wastegate actuator.
I was only boosting 15 lbs with the tune.
I turned up the boost 10% and I'm hitting 20 now.
Added a little fuel and I'm close to keeping it out of COT
Mods are: Stage 2 W\Toys, DCR T body, 3" catless downpipe,(Stock exhaust) ported E mani, big wheel stock turbo, DSP 93 tune.
I have a computer to datalog, just need to do it.

Have you upgraded the fuel pump?

[Mopar318]

I bet the stock fuel pump could handle quite a bit if the injectors are large enough to keep the duty cycle down. I ran about 450hp in my Dakota on a stock fuel pump, along with a booster pump that increased pressure to the rail. That means the in tank pump had enough volume to supply, just not enough pressure for the little 24# injectors at 100% DC.

I think a lot of people over do it with a fuel pump first, then the car runs pig rich due to increased pressure and lack of tuning.

[contraption22]

I bet the stock fuel pump could handle quite a bit if the injectors are large enough to keep the duty cycle down. I ran about 450hp in my Dakota on a stock fuel pump, along with a booster pump that increased pressure to the rail. That means the in tank pump had enough volume to supply, just not enough pressure for the little 24# injectors at 100% DC.

I think a lot of people over do it with a fuel pump first, then the car runs pig rich due to increased pressure and lack of tuning.

Your in tank pump wasn't doing nearly as much work as it would have without the booster pump. More volume of fuel was passing through it because the work of making pressure against the regulator was devided accoss two pumps. Your stock Dakota pump by itself could not have supplied enough volume for 450hp.

[Keito]

No fuel pump upgrade.
I don't think I'll get one, I would first get a set of Duster360's big injectors
He includes a rescale for them along with a rescale for E85:eyebrows:

[ScottD]

I've thought about adding a catch can for a while. I should probably do that as well.

I asked about the fuel pump because of all the threads on SRT forums about doing a fuel pump re-wire. I'm not convinced the fuel pump re-wire isn't just a band aid for a weakened pump.

I'm also not sure how great these 2000s era pumps are. Sometimes my SRT-4 will not crank right away. I know Pat on his Dakota is having the same problem, and I don't think the design of these pumps is the greatest with the regulator and fuel filter in the tank. My understanding is if the pump is not optimal the SRT-4 computer will pull timing, is that correct?

[Mopar318]

I've thought about adding a catch can for a while. I should probably do that as well.

I asked about the fuel pump because of all the threads on SRT forums about doing a fuel pump re-wire. I'm not convinced the fuel pump re-wire isn't just a band aid for a weakened pump.

I'm also not sure how great these 2000s era pumps are. Sometimes my SRT-4 will not crank right away. I know Pat on his Dakota is having the same problem, and I don't think the design of these pumps is the greatest with the regulator and fuel filter in the tank. My understanding is if the pump is not optimal the SRT-4 computer will pull timing, is that correct?

Mine does the same thing. With the stock 1st gen pump, and the SRT pump. Sometimes it will crank for a few seconds longer than usual.

[contraption22]

My SRT-4 does the same thing.... but not consistently. Oddly enough, mine was sitting in my driveway for more than a week before I fired it up this past Sunday and it fired up on what felt like the first crank rotation. That was very unusual.

[Keito]

Don't forget all 3 of our cars are stage 2.
When my car had stock computer, it fired instantly, stage 2, it has to crank for a few seconds.
Every 2 years I have E check and have to throw the stock computer in it, always starts faster.

[contraption22]

Don't forget all 3 of our cars are stage 2.
When my car had stock computer, it fired instantly, stage 2, it has to crank for a few seconds.
Every 2 years I have E check and have to throw the stock computer in it, always starts faster.

You mean they can fail you because your car takes a few extra revolutions to fire up?

[ScottD]

Don't forget all 3 of our cars are stage 2.
When my car had stock computer, it fired instantly, stage 2, it has to crank for a few seconds.
Every 2 years I have E check and have to throw the stock computer in it, always starts faster.

I heard about the starting issue w/ Stage 2 but didn't experience it til sometime after I had Stage 2 installed, probably for the first year or two w/ Stage 2 I didn't have any slow starting issues.

[Keito]

E chack fails because the Stage 2 w/ Toys computer uses a PT Cruiser Automatic PCM.
This throws a code saying the Automatic transmission is having problems, because it's not hooked to the transmission.
The engineers used the auto PCM because they needed more memory for the extra programming for the toys
N2MB has a code scrubber you can wire in to eliminate the code, I just figure switching the PCM is free.

[contraption22]

E chack fails because the Stage 2 w/ Toys computer uses a PT Cruiser Automatic PCM.
This throws a code saying the Automatic transmission is having problems, because it's not hooked to the transmission.
The engineers used the auto PCM because they needed more memory for the extra programming for the toys
N2MB has a code scrubber you can wire in to eliminate the code, I just figure switching the PCM is free.

Ahh. I use the code scrubber. Works great. If the PCM were in a more convenient location to swap out, I might have gone that route, but to swap out the PCM, Injectors, MAP and TIP, drive the car till the it's "ready" for testing, then swapping it all back when I am done would kinda suck. Especially since in PA inspections are annual not bi-annual.

Plus it makes me feel like I am pulling one over on the EPA. And that is a satisfying feeling for me. :)

[Mopar318]

No testing here in Indiana. That makes me happy to live here. They would plug the scanner in a read a 2005, which wont jive with the 98 model it is registered as.

[contraption22]

No testing here in Indiana. That makes me happy to live here. They would plug the scanner in a read a 2005, which wont jive with the 98 model it is registered as.

Yeah for OBDII cars, all they do is check that there is no codes. Doesn't matter that my car has no cat, or anything. All they know is the computer is happy.

[Mopar318]

Yeah for OBDII cars, all they do is check that there is no codes. Doesn't matter that my car has no cat, or anything. All they know is the computer is happy.

Do they check for working ABS? Because I have a code for ABS malfunction...I think it might be because its not there.

[contraption22]

Nah they don't. In fact, my dad's Blazer has had the ABS light on for as long as I can remember and it always passes inspection.

PA inspection is weird. In fact, a car can fail for inoperative fog lights, even if they were only an option on that car. When I worked at a shop, we had a NewBeetle come in with a broken foglight. The parts to fix it were several hundred dollars from VW and the owner didn't have the money to spare. My brother who was a certified PA inspection instructor suggested that we just remove both foglights, because then under PA state code, it would pass.

[Mopar318]

Nah they don't. In fact, my dad's Blazer has had the ABS light on for as long as I can remember and it always passes inspection.

PA inspection is weird. In fact, a car can fail for inoperative fog lights, even if they were only an option on that car. When I worked at a shop, we had a NewBeetle come in with a broken foglight. The parts to fix it were several hundred dollars from VW and the owner didn't have the money to spare. My brother who was a certified PA inspection instructor suggested that we just remove both foglights, because then under PA state code, it would pass.

I lived in PA for 2 years, but since I was just attending school everything was registered in Indiana. I know from friends they had some pretty dump inspection rules, but it seemed to keep the junkers off the road that had rusty brake lines.

I did get pulled over once for not having my lights on while operating my wipers.

[Keito]

Ahh. I use the code scrubber. Works great. If the PCM were in a more convenient location to swap out, I might have gone that route, but to swap out the PCM, Injectors, MAP and TIP, drive the car till the it's "ready" for testing, then swapping it all back when I am done would kinda suck. Especially since in PA inspections are annual not bi-annual.

Plus it makes me feel like I am pulling one over on the EPA. And that is a satisfying feeling for me. :)

Next spring I'm due for an another test, I think I'm going to invest in the scrubber.
I'm afraid I'm going to end up breaking PCM wires pulling them in an out so many times.

[ScottD]

Here in MD I have gone through emissions testing twice with the Stage 2 installed, no issues.

I wish I didn't have to drop the downpipe to install the wideband, otherwise I'd be more motivated to get the DSP and wideband installed before Cecil in November.

[Pat]

Here in MD I have gone through emissions testing twice with the Stage 2 installed, no issues.

I wish I didn't have to drop the downpipe to install the wideband, otherwise I'd be more motivated to get the DSP and wideband installed before Cecil in November.

Why do you? A wideband shouldn't be that close to the turbo anyway due to the heat.

[ScottD]

Based on the how to I read on SRTForums (perhaps this was my mistake) http://http://www.srtforums.com/forums/f75/how-install-aem-uego-wideband-210014/ (http://www.srtforums.com/forums/f75/how-install-aem-uego-wideband-210014/) the downpipe needs to come off. It makes sense to me that it would need to come off to weld the bung on.

The how to notes: "AEM recommends it to be 36 inches away from the turbo and always before the cat for best results, this is where us catted guys are screwed, there is only one option and that is between the flex joint and the cat, this area is only about 16” away from the turbo but we really have no choice".

[Pat]

Based on the how to I read on SRTForums (perhaps this was my mistake) http://http://www.srtforums.com/forums/f75/how-install-aem-uego-wideband-210014/ (http://www.srtforums.com/forums/f75/how-install-aem-uego-wideband-210014/) the downpipe needs to come off. It makes sense to me that it would need to come off to weld the bung on.

The how to notes: "AEM recommends it to be 36 inches away from the turbo and always before the cat for best results, this is where us catted guys are screwed, there is only one option and that is between the flex joint and the cat, this area is only about 16” away from the turbo but we really have no choice".

Forgot about the flex joint before the cat.

[ScottD]

It's just not a job I look forward to doing. The car had under 15k on it when I did the Mopar cat back and the stock exhaust was kind of a pain to get off at that point.

[contraption22]

Taking the downpipe off was pretty easy for me and I had alot more miles.

I would recommend just getting the Mopar downpipe if it is still available. Pricey, yes but it still looks like you have cat, and there is a resonator that makes it more quiet than most catless downpipes. Plus it's Borla quality.

If you are not interested in the stealth looks or sound control, some have had good luck with the Ebay catless pipes.

[ScottD]

It looks like Modern Performance has the Mopar catless downpipe. I already have the Mopar cat-back so this would be a good mod. Good idea Mike.

On the Mopar piece, it looks like there is one bung in it already behind the flex joint and in front of the resonator. I suppose I could use that for the wide band and then put another bung in behind the resonator for the downstream 02 sensor.

Thanks for all the feedback in this thread, it has given me good food for thought.

[Keito]

Wait till you try to run the cable to the sensor.
There's no place I found in the firewall.
I ended up making a very small slit in the shifter boot and running it through there.
If I remember right, there's a plate on the underside I had to loosen, make the slit, run the cable and reattach the plate.
It's still watertight.
I run a Maxxfab catless D pipe, so I used the bung for the cat 02 and have the cat 02 tied up under the car.

[ScottD]

I run a Maxxfab catless D pipe, so I used the bung for the cat 02 and have the cat 02 tied up under the car.

Do you have any issues from not having the cat 02 sensor hooked up? I was thinking even with a catless downpipe wouldn't the factory downstream 02 need to be in the downpipe somewhere?

[Mopar318]

Do you have any issues from not having the cat 02 sensor hooked up? I was thinking even with a catless downpipe wouldn't the factory downstream 02 need to be in the downpipe somewhere?

The downstream O2 only reads the efficiency of the cat, so leaving it out of the exhaust usually has a better chance of not throwing a code than in the exhaust. o2 sees clean air on the outside and thinks the cat is working.

[1qk4dr]

Any dyno numbers or 1/4 mile times with mph?
I have the items you want already installed into my car
such as dsp, duster360 1025cc w/tune, aem wideband, 255 pump, and agp mini.


My SRT-4 has the following mods:

- Stage 2 w/out toys
- Mopar cat-back exhaust
- Mopar short throw shifter
- Motor mount inserts
- K&N drop in
- Toyota Supra PCV valve

I'm strongly considering a DSP and a wideband in the future.

Beyond that, what other mods make sense? Some items I'm considering are:

- AGP direct fit intercooler (I do not want to modify the front fascia, etc.)

- Walbro 255 fuel pump (seems to be a lot of discussion on SRT forums about fuel pump re-wire which may in fact be weak pumps)

- Forward Motion E1 Enforcer turbo

My goals are pretty modest, I just want to maximize the stage 2 that's on there. Thoughts/opinions appreciated.

[contraption22]

Is there a safety concern of having a heated 02 sensor tied up under the car?

[shackwrrr]

Actually the computer wants to see the downstream do the same switching as the upstream but a lesser magatude. Anything that will pull of out of the stream a bit will Millicent this. I've seen aftermarket setups that used a 6 in piece of pipe with a bung on the end welded to the exhaust pipe. You could add a 90and put it parallel to the exhaust.

[ScottD]

Any dyno numbers or 1/4 mile times with mph?
I have the items you want already installed into my car
such as dsp, duster360 1025cc w/tune, aem wideband, 255 pump, and agp mini.

On slicks with the stage 2 in 80-85 deg weather the car has run a best of 13.73 @ 99.4mph. 60ft on that run was 1.84. That day the best mph the car turned was 100.1mph. That's the top mph the car has put down, but not far off the 99.4mph the car put down bone stock at Cecil a few years ago in colder weather but on street tires.

[1qk4dr]

Stock w K&N 14.198@98 mph
93 dsp with above 13.9@105
dr's w above 13.35@105.67
3" thermal, agp mini w above 13.35@105.98
E85, 3bar tip and map, 255 pump, duster360 tune w above 13.347@108.51
slicks next??

I gained 33whp with just the dsp 93 can tune
I gained 7 whp and 18ft-lbs with the exhaust and agp mini

The E85 tune is great since I make so much torque down low which makes the car so much fun on the street. I'd compare the car to my pullied ported Cobra down low now. I have the aem wideband also which is a great little wide band since it is easy to read and self calibrates. Get a add a fuse and it is very simple addition. I hooked the o2 sensor before the cat.

If you have any questions I think you're on the same path that I am. I want to go big stock 16g turbo by mole' next though agp is having a killer deal on a 50 trim kit right now.


On slicks with the stage 2 in 80-85 deg weather the car has run a best of 13.73 @ 99.4mph. 60ft on that run was 1.84. That day the best mph the car turned was 100.1mph. That's the top mph the car has put down, but not far off the 99.4mph the car put down bone stock at Cecil a few years ago in colder weather but on street tires.

[1qk4dr]

I am just afraid that the DSP tune won't have enough fuel for my car with the E1 I have on it. It might, but it might not. I won't know till i get a wideband on it.

Smart, I was running a high duty cycle on my stock injectors on the stock turbo and I had to adjust the air fuel on the can dsp 93 tune especially after I added the exhaust and tune. When I didn't have a wideband I did a dyno a/f run then adjusted it safely and checked for knock.

[Keito]

Do you have any issues from not having the cat 02 sensor hooked up? I was thinking even with a catless downpipe wouldn't the factory downstream 02 need to be in the downpipe somewhere?

The Stage computers ignore the cat 02, but you have to have it plugged in or it will throw a code.
They are for off road use only.
Just for reference, my car with Stage 2 no toys went 13.30's with the big wheel turbo, downpipe with cutout,
drag radials and a splash of race gas.
After I added the toys and a higher mix of race gas, 12.90's
These cars love octane, even when all I had was a catless downpipe, I threw in a couple gallons and went 13.80's
I've used race gas a dozen times, had excellent results, when I'm done racing I fill up the tank with 93 and haven't had a problem with the 02 sensor, since everyone says it will kill them.[COLOR="Silver"]

---------- Post added at 07:44 AM ---------- Previous post was at 07:43 AM ----------


Smart, I was running a high duty cycle on my stock injectors on the stock turbo and I had to adjust the air fuel on the can dsp 93 tune especially after I added the exhaust and tune. When I didn't have a wideband I did a dyno a/f run then adjusted it safely and checked for knock.

Your car wouldn't be an 03 with the smaller injectors would it?
I can't see a high duty cycle with just a stock turbo.

[ScottD]

These cars love octane

The next time at the track I was going to throw some race gas in the car. All my runs so far have been on pump gas.

My understanding is that the unleaded race fuels are not as hard on the 02 sensors as the leaded fuels.

Good thread - thanks for all the replies.

[contraption22]

Unleaded race gas will not harm 02 sensors at all.

[Keito]

My track only has leaded, but my point is running a mix for basically 10-15 minutes isn't going to kill it instantly like most people say.
Make sure after you put a few gallons in it, reset the computer or it doesn't really help.
Theres a fuse you can pull instead of unhooking the battery. I feel that's the key. I also run the downpipe with cutout,
One time I went to the track and opened it up, 13.50 Reset the computer, next pass was a 13.30
Made a huge difference. I'm not sure what was the contributing factor, I assume it's the extreme drop in backpressure?
I can say the cutout is the single one mod that makes the biggest difference, especially if your on stock exhaust like me.

[1qk4dr]

The Stage computers ignore the cat 02, but you have to have it plugged in or it will throw a code.
They are for off road use only.
Just for reference, my car with Stage 2 no toys went 13.30's with the big wheel turbo, downpipe with cutout,
drag radials and a splash of race gas.
After I added the toys and a higher mix of race gas, 12.90's
These cars love octane, even when all I had was a catless downpipe, I threw in a couple gallons and went 13.80's
I've used race gas a dozen times, had excellent results, when I'm done racing I fill up the tank with 93 and haven't had a problem with the 02 sensor, since everyone says it will kill them.[COLOR=silver]

---------- Post added at 07:44 AM ---------- Previous post was at 07:43 AM ----------



Your car wouldn't be an 03 with the smaller injectors would it?
I can't see a high duty cycle with just a stock turbo.

It's an 04 and it was running 92% duty cycle on stock injectors.

[contraption22]

Theres a fuse you can pull instead of unhooking the battery. I feel that's the key.

This is the fuel pump fuse, correct?

[ScottD]

I've gotten into the habit of re-setting the computer every time I go to the track. I used to do this on my T1 Lebaron also when I was racing it regularly.