Warning: Long. Summary toward bottom.

Problem #1:

It seems that every car I own has a few issues in the drivability department that take work on my part to get rid of. My 2007 G35 sedan was no different.

I, like many people, hate the clutch action. The contact point is very small and the throttle control simply isn't very precise.

Now, either one of those is manageable, if you have a normal clutch bite size and a less precise throttle, you can compensate throttle imprecision with clutch actuation and vice-versa. If a clutch bite point is going to be tiny, that's fine if you can have very precise control of the rpm.

Well the 2007 sedan G35 has a quite narrow bite point and poor rpm control (I will call this throttle response for the rest of this review). This first led me to play with the clutch mechanics and I did a few of those clutch modifications (removing the spring, trying to get the clutch closer to the floor, adding a clutch stop) and really the only thing that has helped has been modifying my own driving. My previous car had a clutch bite point very close to the floor and I had 4 years of skill built up based around that feel. This is entirely new. The clutch is fully disengaged about an inch and a half from it's upper limit, on a pedal with about 4-6 inches of travel.

Problem #2:

My second major complaint about the car (and the last one, this car is frankly awesome otherwise) is how NEUTERED it sounds. Too quiet. So I was also searching for a way to get it to reveal some more of it's character acoustically. I listened to tons of sound clips and decided that the stock exhaust with some high flow cats would be the best combination for my personal taste. No artificial sound tuning, just more of the car's natural noise (sorta, I know that the muffler does some acoustic tuning).

Solution for #2:

So I had a mechanic install a pair of Berk HFCs and while it did help the noise department, it hurt the throttle response even worse. Everytime I tried to ease off the line the engine would ignore every input as I let out the clutch, causing the engine to bog or worse, until i gave it so much throttle the engine would suddenly surge, then I would let off a little, still surging, a little more, still surging, a lot more, then bog UGH. The only way to get moving from a stop smoothly was to either launch the car or take it extremely slowly. Also, I was throwing CELs every time I drove them no matter how many times I did the pedal dance.

In the upper RPMs the car was a joy, it had more punch, but I don't spend most of my life in the upper RPMs, I spend most of it shifting and pulling away from stop lights and the constant choice of either bogging, slipping the clutch excessively, or launching from every light was not exactly what I had in mind when I bought a sport luxury car.

Solution for #1

It was time to get a tune. I decided to go to Church Automotive in Long Beach. Shawn Church is a savvy business man and fit me in when he really didn't have to. "Never turn down a paying customer" he said.

The first run on the dyno showed where some of my problems were coming from: The cats were making me run extremely lean down low. Something around 15 afr.

On the positive side, he said the cats alone had given me 20 hp. He has the type of dyno that will bolt directly to your hub. This means that the engine does not have to work to spin the wheels and (in my opinion) gives a better read off of how a particular mod may be affecting your engine. Although, since they do not take into account the tire-contact and the type of wheel you have, they may not represent best what will happen on the street.

Anyway, even with those funky numbers I was making 306 hp at the hub. Three hundred and six, I couldn't believe it. These engines are supposed to make 306 at the crank, and I was doing it at the hub. I should note that I think conditions were perfect for creating power. Church automotive is right AT sea level and it was a nice cool day, with moderate levels of humidity (love california). Anyway, that meant that my cats had effectively counteracted my drivetrain losses. He told me that means the cats had given me about 20 Hp. 2 hours and many runs later he had optimized the AFR, taught me a lot about my car, unrestricted the butterflys (butterflies?) raised my rev limit and given me the 5 maps I had asked for (tuned, economy, stock, Valet, Anti-theft).

Took it for a test drive and was very relieved to find that it had very much helped the trashy throttle response down low. It wasn't perfect by any stretch of the mind (not even as good as my old E36 BMW which is generally considered to only have above average throttle response, not great), but it was at least derivable now.

Shawn then told me about how auto manufacturers are increasingly making their cars ignore small rpm adjustments because they waste fuel. This really irritates me because when you're trying to get the perfect clutch engagement you often (always!) need to be making small 500 or lower RPM adjustments as you go. Ignoring those is like telling the proverbial brain surgeon to use the proverbial butter knife instead of a scalpel. Frustrating. At least its much more responsive down low and in the middle. It drives like a real car now! I don't know what else to say.

Oh and he freed up 10 more hp so I'm making 316 at the hub, a total of about 30? more than stock.

When I get home I'll attach the scans of my final dyno chart. For now you'll have to be happy with a picture of my car on the dyno.


tl;dr: Didn't like the way my car sounded or how it drove, HFC+Tune made it sound way better and made it way more derivable for less than $1k.

Now, while my car DOES sound better overall, around 4000 RPM there is this really tinny almost high vibration rattling sound that does come out. It gets drowned out by engine noise above 5.5k but it's still really annoying.

I asked Shawn Church about it and he said I might have a leak. With that in mind I crawled under my car and checked out the bolts. ONE of my bolts on each cat apparently is missing a head! There's the bolt, the nut, but there's no head on the nut. This is on the upper side of the cat where there is a triangular flange and should be three bolts total. The second picture shows what I mean. You can see the silver bolt and nut, but the brown bolt has a nut and no head. Is this normal? Do these cats only need two? Right now I'm thinking that at RPM this is causing my leak and noise. I'm going to take it back to the mechanic with two more bolts and ask him whats up.

 

That's freaking awesome I have Berks tps and and exhaust I'm planning getting it tuned soon , real excited to see what I get

 

How does the Berk exhaust sound?

 

Whoops i meant to say ark exhaust my bad

 

I'm trying to sell my test pipes right now !!!

 

Would u happen to know anyone who wants tps Ik they give u more power than the hfc and some more growl

 

It's perfectly normal for a threaded stud.

BTW, Great numbers, but I think his dyno may be a tad optimistic

 

^ whs, that one bolt is threaded from factory and those numbers are in fact 'optimistic' since every dyno reads differently, realistically speaking if comparing to other dynos that have same mods and tune you would be around ~280-290whp since you have MT which has lower drive train loss.