Custom Exhaust Question

[JsEvoX]

Has anyone experienced a drop in boost after putting on a new exhaust?Â* I have a friend who wants to do custom exhaust on my evo x but says that there may be an initial drop in boost because the car will be flowing better and that to fix it we'll just need to bring the boost up to normal... Anyone have an idea of what a stock Evo X boosts?Â* Thanks so much!

[KT Motoring]

There may be an initial drop in low end boost response due to the extra exhaust flow which puts less back pressure on the turbine of the turbo. But the drop really is not that significant. What is more likely to happen is an increase in boost pressure due to the increased exhaust flow at higher engine loads.

[JsEvoX]

Thanks, so if the drop isn't that significant then you wouldn't suggest doing anything to try and get that low end boost back right?

[osolokes213]

if you plan to do a few more mods then wait until you actually do them, then go get a tune...if exhaust is all you ever plan to do then you can go get tuned right now...Tha Shop should be able to help you out O0

[Mike W]

Boost by its self does not make power. Boost makes more airflow, and that makes power. So if you do a modification to the car that makes more airflow (say swapping a restrictive part for a less restrictive part) then you get more power, possibly with less boost.

Say you have a garden hose flowing water. Put your thumb on the end and say to your self, "wow, look at all the pressure I have in the hose!" But what happens to the flow? It is less. So you take your thumb off the end of the hose. OMG! I lost perssure! But your flow went up. Flow makes power.

This is also how a larger turbo with a larger exhaust wheel makes more power at a lower boost level. Dont get caught up in a boost number. Remember, the boost pressure number is Bigger pipes will flow more air and more air flow through the motor will make more power.

Mike W

[JsEvoX]

Thanks Mr Real, you're right. Also, thank you Mike W... I lol when I read your example about the water hose. I get it now!!! :grin: How many people change out their stock evo turbo for a larger one?

[Mike W]

How many people change out their stock evo turbo for a larger one?

All the cool kids are doing it these days. WOW nerds that live with their moms still... not so much. Are you GSR or MR?


Mike W

[JsEvoX]

I have a GSR manual. Do you own an Evo?

[Mike W]

I have a GSR manual. Do you own an Evo?


89 Mirage and a '64 VW truck. I have a little Lancer RalliArt that I borrowed though. Why?

Going big turbo knocks over a lot of dominioes, about $3,500+ worth of dominoes. You get some lag and some more top end. Through the middle power stays about the same. On 91 the pistons and rods are still mostly safe. Beyond 400 whp you are on borrowed time. Here is my list of recomendations for a GSR:



EVOX GSR 350hp max goal

Step One 310-330 WHP

Cosworth Drop in filter $43
Real 3� Cat Back Exhaust $600-$800
Some kind of cat option $150-$280
Tune $500

~$1300-1650

Step Two 340-360 WHP

3.5� ETS FMIC $600
Upper and Lower I/C Piping $510
Install FMIC and Pipes $200
Short DP if you didn't have a cat $190
Install DP $ 40
Cosworth Cams $975 installed
Retune $200

~$2700


No BOV, No short shifter, no injectors, no fuel pump. The turbo, injectors and fuel pump are all nicely at their limit. If you have a cat of some sort, stay with the stock DP.



EVOX GSR 400hp max goal

Step One 310-330 WHP

AEM Intake $320 installed
Real 3� Cat Back Exhaust $600-$800
Some kind of cat option $150-$280
Tune $500

~$1570--$1900

Step Two 340-360 WHP

3.5� ETS FMIC $600
Upper and Lower I/C Piping $510
Install FMIC and Pipes $200
Cosworth Cams $975 installed
Retune $200

~$2500


Step Three 400 WHP 91 Octane

Biggee Turbo (Garrett 3076, CBRD BBX) $1800-$2200
AMS Wide Mouth Long DP $475
Install Turbo and DP $700
Walbro Fuel Pump $80
Blaqops Fuel Pump Kit $175
Install Pump and Kit $120
Injector Dynamics or Deatschwerks Injectors $500
Install Injectors $40
Retune $300

$4190-$4590


Beyond this, for more power you really really should be looking at pistons and rods. All the same things that make the EVO X make more power than the EVO 8/9 up to this point, will conspire against you beyond this point. Simply running E-85 at this power level will put you close to 500 WHP on the stock appearing turbos. There is nothing confidence inspiring about the combination of 400+ HP and the stock pistons and rods when you hold one in your hand.

A clutch upgrade brings with it the possibility of a master cylinder failure.

400-500 WHP Goals:

E-85 Tune
Forged Pistons
H-Beam Connecting Rods
Head Studs
Oil Cooler Upgrade

[JsEvoX]

Dang!!!! I just got blown out of the water lol. Ok, so getting a bigger turbo is only necessary if I want to get to 400whp right? That's when I need to get the Biggee Turbo (Garrett 3076, CBRD BBX)? Seriously, If I got 400whp I'd be happy. I like the idea of how you put it in steps so over time I can acquire the parts and get them installed. Right now I'm going to shoot for the 400whp.

[SAVAGEcorpsman]

Amazing explanation, analogy is right on the dot!

[spdracerut]

To add to what Mike said; the reason the boost drops with an improved exhaust is because of how the stock ECU works. The boost tables are designed to tell the ecu to hit a target 'load'. Basically, it's a torque/hp target. When you put on a better exhaust, the engine can hit that same load/load/torque target at a lower boost level.