I did the GT Haus full cat back system. Did not dyno it, but I noticed a significant improvement. So much so that I did nothing else to the car performance wise. It totally brought this car to life in my opinion.

 

I wish more consumers would perform before and after dynos and not take exhaust vendors claims as gospel. Every end-user that dyno their GT Haus setup has shown dismal numbers. A popular RCF youtuber didn't fare any better than a stock RCF (actually lost a pony or two if I recall right).

If we go back to the time M3 were naturally aspirated a number of people complained after dyno their GT Haus setup lost power! It got so bad in some forums that GT Haus had to respond and they stated it was the consumers fault for not realizing that natural aspirated engines don't do well when you remove back pressure, in other words going catless.

The placebo effect is real! Along with getting auditory stimulus due to the louder exhaust sound it is very easy to think your car's performance has improved but when you put it on the dyno reality kicks you in the shin.

 

All aftermarket exhausts are not created equal so there is some variation possible because their design is different. Borla, for example was 2.5 inches in piping diameter while Invidia is 2.75 inches in diameter. The muffler size is bigger in Invidia as well than the Borla etc.

I don't have before/after dynos, but plan on doing dragy runs this spring. A car pulling hard and revving to redline a lot faster after an exhaust is not placebo effect. I cannot speak to those dynos, but definitely RCF with bolt-ons have proven to go 12.0 - 12.3 and definitely a stock RCF would not dip that low.

 

All I'm saying is numbers don't lie. Trust me I have fallen prey for the "butt dyno" test. Did a tune and really thought my RCF was pulling harder, later put it on the dyno and it was all a different story despite claims by the vendor. I doubt my experience is unique, many in the aftermarket scene fall for the same butt-dyno "feel". Placebo effect is not pseudo-science it is well understood. To state that a car feels like it's pulling harder and arriving at red line quicker is not objective at all, not sound. Doesn't hold a candle to actual dyno testing.

My previous comments are specific to GT Haus as it is very well documented and serves as an ominous sign. It has so far shown a poor track record with end users. I'm not in any way claiming aftermarket exhausts are not adding HP. My main point is that the more end-users verify manufacturers claims with actual dyno test, as a collective we would be holding them to higher standards and discourage nefarious claims overall in this business.

"Caveat Emptor" as they say in Latin.

 

Lets just end any speculation that GTHaus exhaust makes even 1hp more than any other 2.5” dual exhaust, it does NOT. We’ve done several supercharged cars with this exhaust, and it makes absolutely no difference vs any other exhaust.

The only exhaust components that make less than what we have just tested is Novel headers and exhaust…. which are consistently the worst performing, especially when adding a supercharger.

Rafi

 

How about, Port/Clean up the Upper and Lower Intake Manifold? Maybe Polish the TB Too!!!

How about some Hotter Ignition Coils tested too?

I've heard that the Sunoco 93 is some good stuff. Have you had any experience with the Shell V Power Nitro?

Great info for the Lexus! Thanks!!!

 

Rafi has messed around with the intake and throttle body before and my understanding is the results were around 2hp or something not worth mentioning. There was no real benefit.

-Justin
RR Sales

 

According to a Tuner I consulted with, Chevron, Mobil, Exxon and Valero have always produced poor results on dynos and high performance engines tend to knock with these brands based on their experience. Interesting to see RR racing confirming this with their Exxon results.

Recommendation by the tuner is 76, Sunoco and Shell.

Most bizarre thing my RCF cannot take any brand but Shell. If I put any other brand other than Shell V Power my low pressure fuel pump begins to whine. I don't have experience with Sunoco but all the other brands cause my fuel pump to whine.

 

Sunoco is great. The pumps used to have 94 octane standard but that ended many years ago. We even had a local station that had a 100 octane race pump 20 years ago at about $6 gallon. On a Saturday night, the street racers would be lined up around the lot. Sadly, it's just the 93 now but still the best fuel I've used.

-Justin
RR sales

 

I was passing through AZ 4 years ago and saw a gas station that had additional pumps off to the side of the station. These pumps had 3 higher octane level gas. it was something like 95, 100 and 105... I did not look at the prices

 

I have a friend here local who has a RC F. He sent his Upper and Lower Intake manifold to a Head porting shop. They made a cut out to flow it on a Super Flow bench and sent it back with the flow improvement numbers. He gained 12hp. He ran it on the Dyno again 2 days later just to confirm and it made 13hp more again. He's only running Intake, a Tune and full Exhaust. I'm going to ask him if he can send me the Dyno sheet. The IS F's also showed about the same gains. The Dyno shop here is a race shop and been doing Dyno's for along time so it was consistent before and after pulls.

 

Live in AZ, have since 2003...have never seen anything above 91 that wasn't 100+ octane race fuel, and our 91 is ACN (Arizona, California, Nevada) which is even ****tier. Wish we had decent quality gas out here, but we just get straight **** water, I guess at least we don't have to pay Cali prices for this garbage fuel.

 

I use Octane 94 and it is amazing. Definitely, I feel a difference relative to using Octane 91, which is the next lower Octane fuel we have available.

 

i filled up at $5/gal for 91….Cali over here…FML. 🤣

 

Lol. Yup **** water 91 octane is all we get, welcome to Cali. Almost 2 years ago I tried 100 octane race fuel was $10/gallon at that time.