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I'm sure this has been discussed but I just want to get it summed up: what are the basic most bang for your buck power mods on the RS? In Subaru world it was the almighty stage 2, downpipe + tune. What's the equivalent here?
 

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AccessPort or equivalent with e-tune, RMM, catback, external wastegate actuator, step colder spark plugs, low cell / catless DP and upgraded FMIC.

And retune. That will get you a heap of power for not too much cash.


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What performance benefits do you get from the BOV?


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AccessPort or equivalent with e-tune, RMM, catback, external wastegate actuator, step colder spark plugs, low cell / catless DP and upgraded FMIC.

And retune. That will get you a heap of power for not too much cash.


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First off, great question as I'm broken in and ready to schedule my HG... After that, bring on the power! So, what's RMM and FMIC? Also, will the cat-less DP pass emissions?
 

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First off, great question as I'm broken in and ready to schedule my HG... After that, bring on the power! So, what's RMM and FMIC? Also, will the cat-less DP pass emissions?
Rear motor mount - reduces wheel hop significantly. Front mount intercooler- upgrade this for reduced heat soak and better boost at higher temps and revs. Pass emissions? Absolutely not. Bit if you want flames bruv, it’s what you gotta do.


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I'm sure this has been discussed but I just want to get it summed up: what are the basic most bang for your buck power mods on the RS? In Subaru world it was the almighty stage 2, downpipe + tune. What's the equivalent here?
Going through my mods and looking at dyno charts, I'd say pro-tune, WGA and E30 are my top three power getters. The downpipe and meth are next.

Step colder plugs will gain a small amount, as will an exhaust. But like almost all mods, it's not the individual parts that net big numbers. It's the additive effect.

FMIC does not gain you any power. It lowers the intake temps, thus making the air more dense which results in a hotter combustion. So, the intercooler is really just an efficiency part vice a true power adder (like a turbo or E85).

I'm not sure how a rear motor mount "adds" power. It allows you have better traction, but you could also do that with tires or learning how to properly drive the car.

The blow off valve/diverter valve/bypass valve is not a power gaining part as well.
 

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Cobb Accessport (650, can find used cheaper and this is fine to do), e-tune from a tuner (~150) will be the best things to do. I would upgrade the bypass valve (160?) since the stock one is a rubber diaphragm. The BPV won't get you power but will give you peace of mind. The car really wakes up from just the off the shelf Cobb tune. There is an immediate recognizable increase in power throughout the power band. Getting an e-tune from a pro tuner will maximize this.

A new air filter (50) is a good plan for more flow. I run an AEM dryflow. Get a closed end filter or you'll deal with whooshing from the intake. I replaced the flexpipe on the intake with a mountune elbow (75?) to smooth it out. The stock intake is pretty good. On a budget, I wouldn't bother replacing the entire intake.

I would do a catback exhaust OR a catless downpipe. Doing both will not be the most effective use of your money. There is a good amount of power to be gained with either, but not much extra is gained by doing both. Stratified has a blog about this. The catless DP (350) would be the best bang for the buck. However, I will be doing catback (800) for the sake of emissions/not getting hassled.

A lot of tuners are saying the stock wastegate actuator should be fine until you add things like meth/e30/etc. There are threads about this on here with empirical data on the wastegate duty cycle.

Step colder plugs (30) are cheap but there are threads on here saying the stock plugs are the same heat range as the "step colder" plugs. I would take your tuners advice on this. Plugs are cheap so not a huge deal to swap them out.

The rear motor mount (150) is not as vital as it was in the Focus ST. I did not notice much change swapping to the mountune rear mount. However, I did this pre-tune so with added power it may be a good idea. Intercooler with hard pipes (800) would also be a good idea to swap out but at the cost I am not sure if it is absolutely vital unless you are tracking. It will give you more consistency and certainly is not a bad idea...but since we're talking bang for the buck I'm leaving it out. The stock IC isn't terrible.

TLDR-

DO:
Cobb AP
E-tune
Catback OR catless downpipe
Air filter

DON'T BOTHER:
Wastegate actuator
Catback and catless DP together

IF YOU HAVE THE CASH:
Intercooler

RECOMMENDED NON-POWER MODS
Mountune Shift arm
Solid shift cable bushings
Rear motor mount
Bypass valve


You're going to get a million different opinions. Do a little research on here. There is some great data floating around.
 

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FMIC does not gain you any power. It lowers the intake temps, thus making the air more dense which results in a hotter combustion. So, the intercooler is really just an efficiency part vice a true power adder (like a turbo or E85).

The blow off valve/diverter valve/bypass valve is not a power gaining part as well.


An aftermarket FMIC certainly does gain you power. That colder, more dense charge brought in through your big ole aftermarket FMIC increases the chooch factor of the incoming air. Colder air = more power. That's why a forced inducted car (and a naturally aspirated car for that matter) feels faster to drive on a cold day. The aftermarket FMIC keeps a better handle on the intake temps of a modified RS because it's larger and more efficient than the factory FMIC. You make more power on back to back runs or longer duration runs (top speed) with the aftermarket FMIC.

An aftermarket blow off valve can potentially gain power due to the OEM valve lifting/cracking/failing at high boost levels. Replacing the plastic OEM valve with a nice aftermarket unit will allow you to crank up the boost (if you have a tune to go along with it). If you cranked up the boost on the factory valve you could be sending extra ponies out into the atmosphere without knowing it.
 

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FMIC does not gain you any power. It lowers the intake temps, thus making the air more dense which results in a hotter combustion. So, the intercooler is really just an efficiency part vice a true power adder (like a turbo or E85).
Correct, a FMIC by itself doesn’t add power it allows you to maintain the cars current power longer by keeping the IATs lower so the ecu doesn’t have to pull timing and boost. Don’t think you would really notice any difference in a daily driven street car, track days, absolutely.
 

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Discussion Starter #11
What are the main bang for the buck power mods?

Thanks @Fordian, that was an excellent run down. I want to clarify a few things. I don't want to go catless, is it going to be more beneficial to go with a catted downpipe or a catback exhaust?

Second, is the FMIC actually going to be helpful on the street? The stock one seems massive to me as it is. I absolutely believe it can heat soak on a track.

Third, Mountune seems to push a lot of this replacement piping stuff. Does that really do much?
 

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Thanks @Fordian, that was an excellent run down. I want to clarify a few things. I don't want to go catless, is it going to be more beneficial to go with a catted downpipe or a catback exhaust?

Second, is the FMIC actually going to be helpful on the street? The stock one seems massive to me as it is. I absolutely believe it can heat soak on a track.

Third, Mountune seems to push a lot of this replacement piping stuff. Does that really do much?
Not a problem. I am by no means an expert but my plans have been to make a strong daily driver without wasting money on unnecessary parts so I've done a good amount of research.

1) I would imagine that the catback would be your better bet here since the catless dp vs catback made similar gains. I would expect a catted DP to make slightly less power. The catback/stock dp will sound better than stock catback/aftermarket dp.

2) The FMIC will be helpful on the street. It's just a question of it being worth the money. If you're on a budget I would skip it. A lot of people are taking off the blanking plates which can drop intake air temps another few degrees (there is data on here as well).

3) I'm not sure what you mean by piping. Cold air intake? Intercooler hard pipes? The stock intake is pretty good from what I read. Can you pick up a few hp in your tune with a full intake? Probably. Is it worth 300-500 dollars? Probably not. The only poor flow component of the stock intake is the flexpipe just to the left of the air filter. That is the piece I replaced.
 

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Discussion Starter #13
3) I'm not sure what you mean by piping. Cold air intake? Intercooler hard pipes? The stock intake is pretty good from what I read. Can you pick up a few hp in your tune with a full intake? Probably. Is it worth 300-500 dollars? Probably not. The only poor flow component of the stock intake is the flexpipe just to the left of the air filter. That is the piece I replaced.
I guess it's the IC hard pipes - https://www.mountuneusa.com/mountune-Focus-RS-Induction-System-p/2536-is-aa.htm
Seems to be about two hundred bucks of extra intake tubes apart from the actual air intake itself.
 

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An aftermarket FMIC certainly does gain you power. That colder, more dense charge brought in through your big ole aftermarket FMIC increases the chooch factor of the incoming air. Colder air = more power. That's why a forced inducted car (and a naturally aspirated car for that matter) feels faster to drive on a cold day. The aftermarket FMIC keeps a better handle on the intake temps of a modified RS because it's larger and more efficient than the factory FMIC. You make more power on back to back runs or longer duration runs (top speed) with the aftermarket FMIC.

An aftermarket blow off valve can potentially gain power due to the OEM valve lifting/cracking/failing at high boost levels. Replacing the plastic OEM valve with a nice aftermarket unit will allow you to crank up the boost (if you have a tune to go along with it). If you cranked up the boost on the factory valve you could be sending extra ponies out into the atmosphere without knowing it.
You and I are not in disagreement on HOW the IC works. I think it's semantics. The power increase is not gained, IMO, it's freed. Also, an increase in core size could introduce a pressure drop, negating any IAT decrease.

The BOV/BPV in of itself is not going to show any power increase. Yes, if the stocker is failing or unable to handle the pressure, then a better unit is needed. But take a bone stock RS, slap in a BOV and you won't see a bump in power. Please show me otherwise if I'm wrong...I'm open to having my mind changed.
 

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What are the main bang for the buck power mods?

Going through my mods and looking at dyno charts, I'd say pro-tune, WGA and E30 are my top three power getters. The downpipe and meth are next.

Step colder plugs will gain a small amount, as will an exhaust. But like almost all mods, it's not the individual parts that net big numbers. It's the additive effect.

FMIC does not gain you any power. It lowers the intake temps, thus making the air more dense which results in a hotter combustion. So, the intercooler is really just an efficiency part vice a true power adder (like a turbo or E85).

I'm not sure how a rear motor mount "adds" power. It allows you have better traction, but you could also do that with tires or learning how to properly drive the car.

The blow off valve/diverter valve/bypass valve is not a power gaining part as well.
You can absolutely make power with an IC. The car pulls boatloads of timing with IAT > 100*F. Where I live, that's a regular occurrence. Need a tune to fully unlock it.


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Correct, a FMIC by itself doesn’t add power it allows you to maintain the cars current power longer by keeping the IATs lower so the ecu doesn’t have to pull timing and boost. Don’t think you would really notice any difference in a daily driven street car, track days, absolutely.
You must not have an AP. I can see timing pulled all the time on the street as ambient temps come up.


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Psssh Psssh, when rolling into a C&C.


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You summed it up with your OP, a stage 2 tune with a Downpipe and an intake is all the RS really needs, the rest is kinda just filler. May I suggest the Revo stage 2 tune, Scorpion catted downpipe, and Mishimoto intake.
 

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What are the main bang for the buck power mods?

You summed it up with your OP, a stage 2 tune with a Downpipe and an intake is all the RS really needs, the rest is kinda just filler. May I suggest the Revo stage 2 tune, Scorpion catted downpipe, and Mishimoto intake.
DP doesn't make any power on this platform, nor does intake. Filter, sure. Tune and FMIC. YMMV


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