JHM Tune, Gutted Cats & Intake Manifold Spacers... your thoughts

[x4frnt]

Is anyone running a JHM tune, gutted cats, and intake Manifold spacers? I'm trying to determine how much power I'm looking at with a combination of just those three things.

[Dolphin S4]

~30hp + ~50% better throttle response from no heat soak and tune.

Worth it.

[x4frnt]

Awesome, that's what's I was hoping to hear

[BCsniper]

I did have that......at one point.

It's probably the best bangs for your buck you can do after getting a catback

[q_dubz]

when you get it, log it blocks 003, and 031. Then send it to me.

[ZimbutheMonkey]

No, you're not going to see 30 HP with gutted cats and a JHM tune.

In terms of outright power delta, the JHM tune only addresses ignition and fueling. It doesn't change the cam timing to my knowledge.

Why it doesn't I have no idea, but my observations of my own car with catless downpipes is that you loose a ton of torque unless you keep the cam lobe angles separated much more than the stock cam tables request.

Also, I don't like gutted downpipes as you're creating a world of headache by making an expansion point right after the exhaust. This will introduce resonant frequencies which can result in reversions at certain portions of the RPM band.

Just spend the whopping $300 and get the SSautochrome ones. I've had them on for some time and have never had any issues with them.

For a tune, I'd recommend calling Steve at Fabspeed. As I've mentioned in numerous other threads. I worked with him on the base calibrations and he knows tuning inside out and backwards.

[x4frnt]

^ great feedback, I'll give him a call for sure. On another note, anyone know what a typical Audi/vw shop would charge to clean my heads and reseat the valves? I could do this on my own, but without another $150 in tools and numerous hours of labor, I believe it would be easier to get someone else to do it (depending on the price involved).

[Mr. Corey]

Stick with the JHM tune its proven and really transforms the car. With a cat-back, DP, Tune, and JHM IM you should be able to put down 300-330WHP

[BCsniper]

Also, I don't like gutted downpipes as you're creating a world of headache by making an expansion point right after the exhaust.

The fact you think gutted pre-cats are a bad idea is ridiculous.

They help you in several different ways and are a free mod you can do in your own garage. Discouraging people from this mod really isn't the thing to do (IMO). You say there is a certain point on the RPM band where there is a possibility of having resonant frequencues......well so damn what? All you have so far is an assumption and we know It helps the car way more than stock for the other 95% of the powerband. Also it gets rid of the air restriction that is put directly after the manifold. The pre-cats main function is during an initial cold-start while the main cars heat up. After that all they do is trap TONS of hot air in our already hot engine bays.

[x4frnt]

^ which is why my pre-cats are being gutted at this moment. Free mod, better sound, and better power. Thanks man.

[ottocycle]

The fact you think gutted pre-cats are a bad idea is ridiculous.

They help you in several different ways and are a free mod you can do in your own garage. Discouraging people from this mod really isn't the thing to do (IMO). You say there is a certain point on the RPM band where there is a possibility of having resonant frequencues......well so damn what? All you have so far is an assumption and we know It helps the car way more than stock for the other 95% of the powerband. Also it gets rid of the air restriction that is put directly after the manifold. The pre-cats main function is during an initial cold-start while the main cars heat up. After that all they do is trap TONS of hot air in our already hot engine bays.

He was comparing piggies vs true downpipes. Piggies introduce strange harmonics with the expansion chamber that used to be a cat. Think two stroke exhaust tuning, as that is what you are essentially doing. Two stroke exhaust tuning on a four stroke motor will give you some strange pulse timing.

[VinnysS4]

I gutted my pre cat's. Now I have a strange harmonic sound coming from the empty cavities that once were cat's. As soon as I let off the gas I can hear what sounds like exhaust pulses getting mixed up. So i feel like gutting them kindof helped power.... maybe a little bit. Would I have done it knowing what I know now about cam phasing and resonant tuning.... probably not. Yeah it's free, but it sounds like crap now. I'll be ordering new DP'S. Just my .02

[Terry.Reese]

So, would it be viable to do just put a straight pipe in place of the precat then?how would the o2 spacers work then? Thanks. I hate drone and would rather not have it in my vehicle but want to get them out.

[x4frnt]

So, this problem could be eliminated by gutting both cats right? But would my tune clear the CEL in that case, and pass emissions? My goal is more power and a better sound, my drawback is extra money to spend after doing the timing chain repair.

[BCsniper]

I gutted my pre cat's. Now I have a strange harmonic sound coming from the empty cavities that once were cat's. As soon as I let off the gas I can hear what sounds like exhaust pulses getting mixed up. So i feel like gutting them kindof helped power.... maybe a little bit. Would I have done it knowing what I know now about cam phasing and resonant tuning.... probably not. Yeah it's free, but it sounds like crap now. I'll be ordering new DP'S. Just my .02

Funny how the other few hundred people who've done the mod didn't experience this issue. The sound is changed after gutting the pre-cats but I would expect so after cutting out that much material. Never did I hear like you're describing.

[x4frnt]

I agree, I've read so many threads and posts about gutted precats and this is the first time I've ever heard this issue. 🤔

[ILVTRANCE]

i got my car with the cats gutted.

car smelled like crap. and pisses everyone off behind you.

[VinnysS4]

Well I'd love for someone to hear it if they are local. I read a LOT of reviews before doing it. Everyone raves about this mod. I understand the logic of getting the heat away from the engine. The car sounds better and feels a bit more responsive, but I will be going with catless downpipes soon with my tranny swap and timing job.

[BCsniper]

I replaced mine with longtube headers. .....the best solution in my opinion

[jr1415us]

I'm running FI 2.5" downpipes that came with metal cats in the pre cat position. Got these used, and I gutted the cats as they were starting to melt and collapse in the center.
So, to address the other comments, there is a huge torque loss around 1200-1800 rpm, the smell is atrocious, and yes, weird roaring sounds when accelerating from a stop.
The only benefit as I see it is subjectively better acceleration at higher speeds.

[x4frnt]

JR, any chance you can get a video with the sound you're speaking of?

[neilpaku]

My wife's car sounds a tiny bit (I mean tiny) more throaty, but doesn't smell any different and seems to drive as usual, with the precats emptied. Still have the main cats.

[DarrenOman]

Gutted my front cats last week. No unusual smell, no strange sound from the down pipes and a little more sound. Wish I had done it earlier and wish it added a bit more throat at full throttle.

If your car is smelling from behind I presume your main cats are shot.

Sent from my SM-G935F using Tapatalk

[Terry.Reese]

So I am going to have this done as well as having my SAI deleted, I will have the o2 spacers installed, won't be able to get the tune to override the CEL for that for a few months, will this hurt the car at all while it is still throwing a code?

[JimmyBones]

No, you're not going to see 30 HP with gutted cats and a JHM tune.

In terms of outright power delta, the JHM tune only addresses ignition and fueling. It doesn't change the cam timing to my knowledge.

Why it doesn't I have no idea, but my observations of my own car with catless downpipes is that you loose a ton of torque unless you keep the cam lobe angles separated much more than the stock cam tables request.

Also, I don't like gutted downpipes as you're creating a world of headache by making an expansion point right after the exhaust. This will introduce resonant frequencies which can result in reversions at certain portions of the RPM band.

Just spend the whopping $300 and get the SSautochrome ones. I've had them on for some time and have never had any issues with them.

For a tune, I'd recommend calling Steve at Fabspeed. As I've mentioned in numerous other threads. I worked with him on the base calibrations and he knows tuning inside out and backwards.

Dude you are either flat out lying or ignorant. The JHM ECU tune does change camshaft timing. There are over 100 changes with the B6/7 S4 tune. I know because I have logged my car and multiple other local S4s.

BCsniper as already addressed gutting the downpipes and I agree with him.

Then your standards for quality may be different than others. I personally want my exhaust to be able come off and go back on without any issues for years. There are always going to be reasons for downpipes to come off for servicing and crappy downpipes usually don't want to cooperate when you try to take them off and put them back on. Can't tell you have many local people have shitty quality downpipes that take longer to deal with than good quality downpipes when they want me to help them. However a good example of quality parts is the set of V1 JHM headers that have been used on my car, then Slow4's car, and now currently geebus's car. Those headers have been used hard for years now and they still work great!

[MantanaB6]

I have a JHM intake manifold, spacers, piggies, and tune. There is a bit of smell off the exhaust, but only noticeable if standing directly behind the car. As far as power goes, I've never really driven a stock S4, but I'd say it pulls almost as hard as my dads B8.5 S4. Also I have a magnaflow exhaust and there is a bit of low speed/rpm boominess, but zero drone while cruising.


Sent from my iPhone using Audizine

[jr1415us]

To clarify, gutted cats on the FI downpipes=no cats. So they stink more than piggies, which retain the main cats.

[ILVTRANCE]

Well I'd love for someone to hear it if they are local. I read a LOT of reviews before doing it. Everyone raves about this mod. I understand the logic of getting the heat away from the engine. The car sounds better and feels a bit more responsive, but I will be going with catless downpipes soon with my tranny swap and timing job.

what dp's are you thinking of going with?

[x4frnt]

So I guess my overall question is; gut my pre-cats or stick with them the way they are. Secondly, what are the odds of encountering a CEL with the O2 spacers? Is there a way to modify the spacers to help avoid a CEL? And can I rid the CEL without getting a tune (not saying I am going to skip the JHM tune, but the tune will come roughly a month after I put my car back together and I need to get an inspection done immediately)

[MantanaB6]

So I guess my overall question is; gut my pre-cats or stick with them the way they are. Secondly, what are the odds of encountering a CEL with the O2 spacers? Is there a way to modify the spacers to help avoid a CEL? And can I rid the CEL without getting a tune (not saying I am going to skip the JHM tune, but the tune will come roughly a month after I put my car back together and I need to get an inspection done immediately)

Maybe just wait to do the piggies until after the inspection? O2 spacers w/ gutted piggies could potentially not give a CEL, but there's no guarantee. Whereas there is a guarantee that with a tune you won't get the O2 sensor CEL. If you must gut your piggies immediately, people seem to have good luck with the J-bend spacers; they come with a variety of fittings to adjust the amount of exhaust they let through, so you can "tune out" the CEL by fiddling with those. People have guesstimated that gutted pre-cats or dp's may also help expelling heat which can potentially aid in preventing various maladies that affect the 4.2 in the S4, so there could be benefits outside of just pure performance increases. But don't quote me on that; somebody with more knowledge of this platform could maybe pipe up about this.

[Terry.Reese]

So I guess my overall question is; gut my pre-cats or stick with them the way they are. Secondly, what are the odds of encountering a CEL with the O2 spacers? Is there a way to modify the spacers to help avoid a CEL? And can I rid the CEL without getting a tune (not saying I am going to skip the JHM tune, but the tune will come roughly a month after I put my car back together and I need to get an inspection done immediately)

Same questions as me, i am also doing a SAI delete which i know will cause a CEL, my question is will that CEL hurt my car at all of it stays on for a while?

[ZimbutheMonkey]

The fact you think gutted pre-cats are a bad idea is ridiculous.

They help you in several different ways and are a free mod you can do in your own garage. Discouraging people from this mod really isn't the thing to do (IMO). You say there is a certain point on the RPM band where there is a possibility of having resonant frequencues......well so damn what? All you have so far is an assumption and we know It helps the car way more than stock for the other 95% of the powerband. Also it gets rid of the air restriction that is put directly after the manifold. The pre-cats main function is during an initial cold-start while the main cars heat up. After that all they do is trap TONS of hot air in our already hot engine bays.

OK, let me rephase this: Having an expansion chamber that necks down right after the exhaust pulse exits the engine WILL RESULT IN A REVERSION IN SOME PART OF THE RPM BAND

If you knew the first thing about pulse resonance tuning, you'd know that this is a BAD idea and that you're much better off ponying up the whole $300 and just getting a 2.5 in straight pipe.

If someone is so broke that they can't afford it, then hey, knock yourself out and make piggies. It will be better than stock.

However the OP is asking what his options are and I'm telling him. If you don't like what i have to say, than go pound sand...

Oh, and does anyone have any logging data for a car with piggies? I'd be interested to the MAF readings from cars with piggies it vs straight pipes.

[ZimbutheMonkey]

Dude you are either flat out lying or ignorant. The JHM ECU tune does change camshaft timing. There are over 100 changes with the B6/7 S4 tune. I know because I have logged my car and multiple other local S4s.

BCsniper as already addressed gutting the downpipes and I agree with him.

Then your standards for quality may be different than others. I personally want my exhaust to be able come off and go back on without any issues for years. There are always going to be reasons for downpipes to come off for servicing and crappy downpipes usually don't want to cooperate when you try to take them off and put them back on. Can't tell you have many local people have shitty quality downpipes that take longer to deal with than good quality downpipes when they want me to help them. However a good example of quality parts is the set of V1 JHM headers that have been used on my car, then Slow4's car, and now currently geebus's car. Those headers have been used hard for years now and they still work great!

Then show me the logs....

Or better yet, why don't you show me a screen shot of winOLS comparing the two...

Have you actually dissected a JHM file? I have.....

Before he passed (RIP) Daz sent me a copy of the JHM S4 file and guess what THE CAM TIMING TABLES WERE THE SAME BETWEEN THE JHM FILE AND STOCK!!!

I know exactly how many maps were changed, and it's not 100's. It's 54 including the smaller 1D and 2D maps;

There are 28 3D maps changed and of those 28 3d maps, 8 are just maxed out torque limiters.

Dude, I know the S4 ECU inside out, sideways and backwards. I've literally spent about 1000+ hours over the last year dissecting and staring at the tables as I developed my own definition file for my 560G ECU. I also have literally hundreds of different revisions for the file that I have now and Gigabytes of logging data that I've poured over.

My job takes me all over the backwoods highways of our Province so when I would go to Court in a far off location, I would set up my bench flasher to run off an inverter, go out and log my car. Stop, tweak the file, reflash the ECU, rinse lather repeat... Sometimes I'd try 5, 7, 10 different versions a day.

So don't think that you know anything even close to what I know about tuning these cars, the simple fact is you don't......

[Jake@JHM]

If you saw a file where the cam timing tables were the same as stock, you didn't see a JHM file.

[ZimbutheMonkey]

If you saw a file where the cam timing tables were the same as stock, you didn't see a JHM file.

Oh, so you're saying that Daz was lying to me?

I've seen logs of your V6 3.0 file and the cam timing tables were exactly the same as stock, for both the intake and exhaust.

Here's the intake and exhaust logs from a JHM tuned Audizine member


Intake and exhaust from my stock ECU


If you have changed them, then someone post up some cam timing logs of a JHM tuned V8.

Until I see some kind of proof, my statement stands.

So, are you going to show me some kind of proof that you guys changed the cam timing tables?

[Jake@JHM]

Do I think a thief lied to you? Certainly. However there is always the possibility that he was the one that was fooled..

[Mr.Wrong]

The fact you think gutted pre-cats are a bad idea is ridiculous.

They help you in several different ways and are a free mod you can do in your own garage. Discouraging people from this mod really isn't the thing to do (IMO). You say there is a certain point on the RPM band where there is a possibility of having resonant frequencues......well so damn what? All you have so far is an assumption and we know It helps the car way more than stock for the other 95% of the powerband. Also it gets rid of the air restriction that is put directly after the manifold. The pre-cats main function is during an initial cold-start while the main cars heat up. After that all they do is trap TONS of hot air in our already hot engine bays.

Dude you are either flat out lying or ignorant. The JHM ECU tune does change camshaft timing. There are over 100 changes with the B6/7 S4 tune. I know because I have logged my car and multiple other local S4s.

BCsniper as already addressed gutting the downpipes and I agree with him.

Then your standards for quality may be different than others. I personally want my exhaust to be able come off and go back on without any issues for years. There are always going to be reasons for downpipes to come off for servicing and crappy downpipes usually don't want to cooperate when you try to take them off and put them back on. Can't tell you have many local people have shitty quality downpipes that take longer to deal with than good quality downpipes when they want me to help them. However a good example of quality parts is the set of V1 JHM headers that have been used on my car, then Slow4's car, and now currently geebus's car. Those headers have been used hard for years now and they still work great!

If you saw a file where the cam timing tables were the same as stock, you didn't see a JHM file.

How dare you guys question ZimbutheMonkey?!?!? Don't you know the almighty protol. First and foremost, you must post your rather impressive complete credentials in an automotive industry, specifically in the department the topic in question is on. These do include your previous employer/s, length of employment, exact position, etc... There's a form somewhere on here. After he'll glance at it and still dismiss everything you posted just to flip you off and move on as a selfproclaimed ultimate expert on a subject matter.

[JimmyBones]

Then show me the logs....

Or better yet, why don't you show me a screen shot of winOLS comparing the two...

Have you actually dissected a JHM file? I have.....

Before he passed (RIP) Daz sent me a copy of the JHM S4 file and guess what THE CAM TIMING TABLES WERE THE SAME BETWEEN THE JHM FILE AND STOCK!!!

I know exactly how many maps were changed, and it's not 100's. It's 54 including the smaller 1D and 2D maps;

There are 28 3D maps changed and of those 28 3d maps, 8 are just maxed out torque limiters.

Dude, I know the S4 ECU inside out, sideways and backwards. I've literally spent about 1000+ hours over the last year dissecting and staring at the tables as I developed my own definition file for my 560G ECU. I also have literally hundreds of different revisions for the file that I have now and Gigabytes of logging data that I've poured over.

My job takes me all over the backwoods highways of our Province so when I would go to Court in a far off location, I would set up my bench flasher to run off an inverter, go out and log my car. Stop, tweak the file, reflash the ECU, rinse lather repeat... Sometimes I'd try 5, 7, 10 different versions a day.

So don't think that you know anything even close to what I know about tuning these cars, the simple fact is you don't......

Why bother posting logs. You are just going to ignore them anyways. See Mr. Wrong's post below for a better explanation.

If you saw a file where the cam timing tables were the same as stock, you didn't see a JHM file.

Do I think a thief lied to you? Certainly. However there is always the possibility that he was the one that was fooled..

As usual Jake's posts are on point.

How dare you guys question ZimbutheMonkey?!?!? Don't you know the almighty protol. First and foremost, you must post your rather impressive complete credentials in an automotive industry, specifically in the department the topic in question is on. These do include your previous employer/s, length of employment, exact position, etc... There's a form somewhere on here. After he'll glance at it and still dismiss everything you posted just to flip you off and move on as a selfproclaimed ultimate expert on a subject matter.

This post is hilarious because it is true.

[ZimbutheMonkey]

Do I think a thief lied to you? Certainly. However there is always the possibility that he was the one that was fooled..

Lol, of course, when I ask for proof, this is what you come back with. Pretty much what I expected, bravo..... (slow clap).

Not likely Daz was fooled, he knew more than you, me, and this whole forum combined when it came to tuning.

Also, shame on you for calling Daz a thief. But anyway, if you want to talk smack about a dead guy who can't respond to your comments (REAL classy by the way Jake ), I guess Ill have to do it myself...

Calling Daz a thief implies that he somehow stole and implemented aspects of your file in his own work. Trust me, Daz didn't need to steal a damn thing from you guys, anyone who knows anyone in the tuning scene knows that Daz could have run circles around you guys in his sleep, period, end of story.

Why do I know this, because unlike your operation, Daz was actually open and forthcoming with what he knew. He was an invaluable asset to the tuning community and we're all worse off for his being gone, can we say the same of JHM?.... no, didn't think so....

PS: I also suppose that the forum member with your V6 tune and supplied the picture above of his logging data (which demonstrates no changes to the cam timing tables) was lying too.

How dare you guys question ZimbutheMonkey?!?!? Don't you know the almighty protol. First and foremost, you must post your rather impressive complete credentials in an automotive industry, specifically in the department the topic in question is on. These do include your previous employer/s, length of employment, exact position, etc... There's a form somewhere on here. After he'll glance at it and still dismiss everything you posted just to flip you off and move on as a selfproclaimed ultimate expert on a subject matter.

No need to flip you off, your handle says it all

[x4frnt]

If someone wants to send me a cable, I'll do a stock vs piggie mapping comparison 😁