Hey Guys,

I finally had a chance to get a set of high flow cats for the Aston. It took me a while to figure out which route I was going to take because I wanted to try something totally new and different that had never been done before. I will explain the entire journey, which took some unexpected turns, but I think is important for the Aston Community to consider for the future potential of our platform. I will follow up with a full review of the Ken Harrison High Flow Cats with some surprising results. I will try to keep it as concise as possible given the large amount in information to cover (I know its lengthy but bear with me, the info is worth it).

Background:

After closely analyzing the stock exhaust system (in conjunction with my previous experience on my last 4.3L Vantage years ago), I wanted to figure out a way to solve the fundamental key design flaws in our exhaust system in the most efficient and cost effective way possible.

The primary design flaw that always bothered me is the lack of an X-pipe in the exhaust design (or any real crossover for that matter). On my previous 4.3L Vantage, I purchased the RPI catback exhaust due to its unique X-pipe design because really liked the idea of having an X-pipe built into the rear muffler. However, There are a few inherent design flaws in this approach. First and foremost, the X-pipe is way too far back in the exhaust system to maximize scavenging effects in the cylinders. Yes, the RPI did make 13HP at the wheels on the top end past 6000rpm, but below that rpm there was virtually no change. Second, removing the stock catback ruins the airflow path to the rear transmission/differential cooler in the rear diffuser. The stock exhaust system performs this task well, which I have yet to see any other catback truly mimic perfectly. On top of that, the RPI was $3400 retail new! Even though I purchased it during a X-mas Holiday special for $1700 (50% off), it still was too expensive in my opinion for what you get (not to mention some minor quality control issues). Furthermore, now that I have proven you can polish up the stock exhaust to an almost perfect mirror finish with just a few hours of effort it made the necessity to replace the rear catback eyesore far less necessary. Also, replacing the entire mid-pipe section just to put an X-pipe in did not make any sense both financially and logically making it seem like a waste of money. Finally, I like the OEM exhaust valve feature to remain intact for future exhaust modifications in case the exhaust got too loud for hwy cruising (i.e. Mild2Wild). For these reasons I decided to keep the stock exhaust and put my money elsewhere this time ... I knew there had to be a better way.

The second major design flaw is of course the stock OEM cats. They are absolutely terrible in every way possible, we all know this. Their 600-cell primary & secondary dual hybrid cat design with secondary oxygen sensor in between the two cat cores is a recipe for premature failure. Not to mention, the cats lifespan is so short and most go out so quickly that upgrading them is more preventative maintenance than a performance modification depending on how you look at it. They are going to fail ... and quickly too. I looked at the various different designs out there and thought how could I fix all the inherent design flaws, while improving exhaust flow all with one single part.

In comes the "X-Cats" ... The X-cat is something I wanted to try this time around but given how nobody had done it before there were a lot of unknowns on whether it would be technically feasible or not. The primary purpose of the X-cat design is to incorporate the high flow cat after the stock headers, immediately followed by a smooth mandrel bent X-pipe. The purpose of this design is to bring the X-pipe as close to the headers as humanly possible to maximized the scavenging effects at high rpms and also to help aid the can in "pulling" the air through the catalytic cores at a faster rate than would be possible otherwise, essentially turning a 300-cell core into a 200-cell, 200 into 100, etc. Given the known gains for catalytic converts and what I made on the X-pipe, it does not seem out of the realm of possibility to make up to 30 crank hp with such a part. It would solve all of the inherent design flaws of the factory system without any of the negative drawbacks of doing so. Even better, on the 2010+ models you do not even need the secondary cats and can completely delete them making this the perfect space to do a high flow X-pipe. This will probably make a good 20 crank HP on the 2010+ V8 (10HP less than on older ones because the stock primaries are still in the headers, but still very healthy gains).

After searching around for a few months to figure out if any local shop could actually do, and I did; it is certainly technically feasible. However, I eventually ran into a few road blocks, mainly price. Everyone wanted $4k+ to do such a project and honestly I did not want to spend more than 3x what the KH cats cost to be the guinea pig. As much as I like being on the modding frontier by being a test car, even this was a bit too rich for my blood for just cats haha. I am posting this experience in hopes that one day one of the forum vendors (aka Stuart @ Velocity) will be able to produce something for ~ $2500. If that is ever the case I will definitely buy them for sure, but for now I opted to go the more conventional cost effective route.

Ken Harrison High Flow Cats:

After browsing what was in the market place, I wanted to try something different and new that had not been reviewed before. Given I was in an experimental mood I wanted to try the Ken Harrison cats. Although initially the lower price appeared to be a red flag (and using ebay as a sales channel), I decided to do more research to learn more about them. After emailing the seller I realized that the owner of the company is actually Ken Harrison himself. I also came to found out that his own personal exotic is a 4.3L Aston Martin V8 Vantage (hence why he used it as a test car for developing the product). As a fellow Aston guy he obviously knew some of the inherent flaws with the Aston cat design and also the potential for Check Engine lights to pop up with aftermarket high flow cats and you can clearly see how well he understands this given the unique design approach he took.

Initially I assumed, based on the price point and sale channel, that these were probably Chinese knockoffs. But, after speaking with Ken directly he proved that they are in fact made right here in the USA in California (sometimes we just a book by its cover for that I retract my previous statements regarding them possibly being Chinese made, lesson learned). After seeing the cats in person I realized immediately there is no way these were made overseas, the quality was simply way too high to be anything Chinese made, so I definitely believe his claims (more on this later).

Quality & Design:

The main reason I chose these cats is I liked their design better than any other cats out there due to a few unique features which I thought seemed superior to a lot of what else was out there. The first thing I noticed is the cats cores are "spun" not welded. If you look at the cats closely you will see the piping smoothly conforms to the cat body in a conical shape without any welds whatsoever. Spun cats always offer the highest strength as there are fewer welds for exhaust gasses to potentially weaken and fail over time. Also, the cats are high strength double TIG welded (both inside and outside) by using a sleeve for added strength. This ensures that the weld of the actual catalytic core is not exposed to the extreme heat buildup directly in front of the catalytic core. This also allows for double welding of both the inside & outside weld seem at the cat flange at the front by the header outlet.

Moving further back, the position of the oxygen sensor intrigued me given their unique placement. Normally the primary oxygen sensor is put directly into the path of the exhaust flow. On the KH cats, they are offset into the conical portion in the pre-cat chamber making it less obstructive to airflow while still being able to accurately read the exhaust gas flow (every little bit of airflow helps at this level). Even more impressive though (and I think the one key differentiating factor between these cats and any other) is the secondary Oxygen sensor port. Every cat I have seen puts the rear O2 sensor after the cat core and sits directly in the path of the post cat piping exhaust flow. The bigger issue is that if you use a 200-cell cat core, there is a decent probability you will throw a CEL with this design (which many do). Normally I thought I would never do a 200-cell cat core, but when I saw these cats I knew that these may actually work. It's not until I received the cats and actually looked into the secondary O2 port that I realized Ken really knows what he is doing. At first I thought the long shaft on the O2 sensor was just an open extension. What I did not realize is they are actually oxygen sensor defouler built directly into the cat itself ... very cool! If you look at the attached pictures you can actually see the small pencil sized hole in the actual O2 bung. I asked Ken if this would throw a check engine by being too small, he said "no not at all, none of my cats have ever thrown a CEL on either my own car or customers cars". Given his level of confidence I realized he knows exactly what he is talking about. Normally you have to buy cheap looking add on extenders or little screw on elbows, but I did not like the thought of such an "afterthought" design, not to mention yet another additional point for leaks to occur. Ken managed to perfectly integrate them and fit in the exact proper location so they O2 sensors are exactly where they should be in a neat seamless design.

Another product design characteristic that led me to chose KH cats was the actual size of the catalytic core itself. All the other cat cores on the market appear to be running 5" cat core @ 200cell. The KH cats run a 4" cat core @ 200cell. As counterintuitive as it may seem, this is actually a positive not a negative. Going from a 2.75" header outlet, to a 5" round cat core can cause turbulence as the gas velocity is having to slow down to both expand, and pass through the core. On the KH cats, the inlet is actually a 2.9" inlet and the 4" cat core is more smoothly shaped (gradual) to force the exhaust gasses through the catalytic core at a higher velocity thereby maintaining better airflow even though in theory the 4" cat core has a lower theoretical max flow rate than a 5" core. This brings up a very important point that shouldn't be glossed over though: How much airflow do our smaller V8s really need? If you imagine our 4.3L (or 4.7L) V8s as essentially two inline fours with separate exhaust systems, you essentially have two 2.15L engines (or 2.35 for the big brother folks). A naturally aspirated 2.15L can only flow so much air, especially given the remainder of the exhaust system is ultimately just 2.5" in diameter. After managing to source exact CFM numbers for the cats, it turns out that a 3" inlet 300 cell high flow cat flows 467 CFM per cylinder bank, and the 200-cell 4" round flows 508CFM PER BANK (multiply by 2 for maximum theoretical amount)! Heck, each cat alone is rated up to 5.9Ls. That is WAY more airflow than our motors will ever need, and it is for this reason why upgrading from a 300-cell to a 200-cell at this size will only next you 1-2HP tops, the motor simply doesn't need it (much less a 5" core @ 200cell). Anyways, I am sure you get the point, the cats are more than ample enough to flow given their design (as proven by the dynos below).

Overall Rating: 9.5 / 10 for quality

Installation:

Installation was a breeze, 3-bolts per side. Use some penetrating lube and let it sit for 10-20 min. The kit game with bolt hardware but I actually chose to retain the OEM factory hardware since it looked stronger than what was supplied with the kit. The cats did not come with factory gaskets so I had to order those for about $40 for the pair. I have told Ken to supply these with the cats in the future for convenience, he said he would definitely look into it. The cats were installed at Eurocharged's huge brand new facility in Houston, and they only charged me an hour of labor, they did an awesome job.

Dyno:

When I previously dynoed my car previous for the V2 tune, it was during the much cooler months of the year (~50F, <20% humidity) so the weather was about as ideal as it got. Now in the dead heat of summer I knew the numbers would not be as high given the terrible weather (95F+ @ 90%+ humidity), not to mention summer blend gasoline is not nearly as good as winter blend. Even with all those factors the new Baseline was only roughly 9HP less than my winter results on the V2 tune! I was very impressed with the consistency of the power given the wide range of weather variation between summer & winter, a testament to the quality of the V2 tune. Add that 9HP differential back in these numbers equate to roughly a peak HP of 384wHP in the winter... no slouch for the ol' short stroke 4.3L (roughly a 60whp gain over stock)! Also, another interesting observation is the Air Fuels have richened up. It was for this exact reason why I intentionally planned ahead and did the V2 tune development in the winter because I knew as the weather got warmer (and thinner) the mixture would naturally richen up versus the opposite scenario if I did it in summer and then it would run too lean in the winter. So for those skeptics who thought the tune may be too aggressive or pushing the motors too hard, this is proof it is not even close to that threshold; the Eurocharged V2 tune really is that safe.

Before & After Dyno were performed the same (only 2 hours apart) for maximum accuracy of the results. The official HP claims made by Ken were 12+ crank HP.... needless to say my car blew those numbers out of the water. The final result was ~ 17HP & 17TQ as the wheels (roughly 20@crank)! Remember, these results are with ZERO ECU adaptation, literally the first run out it did these numbers. I am sure with more adaptation it would pick up a few more but given how consistent all three runs were I would say the gains are immediately noticed. The results were so shocking they even impressed Eurocharged that they have decided to become an official distributor for the cats (totally unexpected outcome). Once they finalize the V2 Stage 2 tune (aka V2-S2) on my Vantage soon they are will sell both as a combo performance package.

The Dyno results are pretty damn impressive given the price-point, but I wanted to dive into more low end to mid-range rpm specifics the actual gains and at what RPM:

2500rpm = 16.5 TQ @ wheels
4300rpm = 15.7 TQ @ wheels
5300rpm = 13.6 TQ @ wheels
7700rpm = 16.8 HP @ wheels

Catalytic Data:

I ran a few tests with the new Autel MD802 I just purchased (full All-systems version, don't get the basic 4-systems) and was able to get more in depth into the engine ECU to get a better idea of how the high flow cats are performing from an emissions perspective. There is one test in particular call the "Catalytic Bank Test 1 & 2". You can literally test each cylinder bank separately with the "Front - Rear Switch Ratio Test". What it essentially does is it tests the ratio between the front and rear Oxygen sensors to essentially see if the catalytic converter is functioning properly as it should. The cool thing about the MD802 is it not only tells you what each cylinder bank is running at, but also tells you the maximum threshold before it triggers a CEL. The higher the number gets, the less effective the cat is doing its job b/c the rear 02 sensor is picking up more emissions than it should be otherwise (lower is better). After seeing the results it became very clear that even with a 200-cell cat, those rear O2 sensor defoulers are doing their job very well!

Right Bank = 0.175 / 0.395 limit
Left Bank = 0.176 / 0.395 limit

3.0" 300 Cell = 467 CFM per bank x 2 = 934 CFM total potential
3.0" 200 Cell = 508 CFM per bank x 2 = 1,106 CFM Total potential ** (KH cats)

Performance:

After Driving the car for over a week now, I can say the tune has definitely woken up the car and finally unlocked the low end to midrange torque I was desperately looking for before. The Eurocharged tune did wonders above 4000rpm for me, but below that it did not do that much for low end torque. On some other forum members cars it appeared to provide a lot more torque with the V2, but on my specific car it did not (every individual car is different, to each his own).

The low end pull at lower rpms is fantastic and finally feels like a 4.7L on the bottom end. Given the numbers it is pulling now this can definitely hand with the bigger 4.7Ls, if not give them a run for their money. I am now spinning the tires on the bottom end in 1st & 2nd with 305s Pilot Super Sports so the torque is definitely no question. More so than anything, I like being able to be in a higher gear at a lower rpm when cruising and accelerating without having to downshift anymore. The throttle response has also improved by roughly 10% and is now much easier to do rev-matched downshifts due to the more free revving blip nature of the less restrictive cats.

Sound:

This was actually one of my biggest fears of doing high flow cats without an X-pipe. The exhaust system is DEFINITELY louder, a good 20% so. But surprisingly it's not "too" loud. I will say if you plan on getting high flow cats I definitely would never get an aftermarket exhaust, it would be waaaay too loud. I really have no idea now people have both, it would seem obnoxiously loud. On the Dyno, the car sounded absolutely amazing above 5000rpm, and above 7000rpm it's a true screamer now. Between 2-4krpm it is a little bit more rougher sounding than before from outside the car, but nothing excessive. Having the Mild2Wild makes this a moot point so it's not as big of a concern. From inside the car, the exhaust sounds awesome now, it has totally changed the character of the car (in a good way) and woken up the performance significantly. Because the video microphone cannot pick up the deeper base tones it's hard to replicate the true sound, but it actually sounds much smoother than the video would suggest. If there is only one exhaust modification you do, this should be it. I would advise against getting a catback, the stock one will do just fine IMO. Can't wait to up the rpms to 7800...

Since I have gotten it back I have put Fuse22 back in just for testing purposes and I realize now I like the option of having the valves closed. I am definitely glad I kept the stock catback given this realization. With the fuse 22 back in, I would say the sound volume is roughly half way between what the stock fuse 22 installed vs. removed. It is definitely quieter than the stock exhaust without fuse22, but certainly more bass with Fuse 22 back in compared to a 100% stock car. The one odd quirk I never realized with the stock cats since they weren't loud enough is the valves actually open up from idle to around 1500rpm then close back up until 3800rpm, where they open back up again. Therefore, when accelerating you get this Loud>quite>LOUD pattern which takes time to getting used to, not annoying, just different. But cruising on the highway with the valve closed is sublime, just a hint more bass tones than before when cruising. You know the sound is more pronounced, and you can certainly feel the added torque cruising in 5th & 6th. Also, at idle when resting with the AC on the exhaust is louder (I am assuming due to increased engine load) then quiets back down when you turn AC off... weird but nonetheless true. Mild2Wild exhaust valve control (integrated into the factory Homelink mirror buttons) is a must in my opinion to have the best of both worlds. I have already ordered & received my Mild2Wild off of Amazon ... that write up will come in the near future...

Price:

Roughly 50% less than RSC cats, you can look them up on eBay for the exact price. They are definitely the best "bang per buck" exhaust modification you can do for our vantages ... other than polishing stock exhaust of course.
Conclusion:

Overall, the cats exceeded my expectations in every way. At first I was very apprehensive about trying a newcomer to the Aston world, especially with cats. However, I can say unequivocally I could not be happier with the results. Given the way the car is now, I don't think I ever want or need another vantage again.

.... Add Headers & Pulley into the mix and I would say it's the perfect Vantage

Hope that helps,
007

 

More Pics...

 

Great write-up I was looking at those a month ago but was hesitant on pulling the trigger because I wasn't sure about the quality of the product, fit and finish and their company experience with our cars. After reading your write-up I feel much better. I would like to also do the Eurocharged V2 tune but I don't see they have any associated shops in South Florida

 

They can send you the remote tuner and you can tune the car yourself in the comfort of your own garage easily. Just ask for their remote tuner. You can buy it or they can send you the loaner tool. Totally up to you. If I weren't local I personally would like to have one on hand always just in case they come out with new versions of the tune and you do more mods in the future. It's nice to have that convenience.

Just email them at sales@eurocharged.com and they can take care of you.

 

Thanks that's perfect. I'll shoot them an email.

 

G'Day,

Where did you buy the Cats, I can't find them anywhere on the net.

Cheers

Christian

 

You can find them on ebay, search "Aston martin catalytic) and they will pop up.

I am sure Eurocharged could order them for you as well if you wanted to get package deal on ECU tune and cats.

With the two combined I have made almost 52 wheel HP, and that's not including the summer vs winter weather. If you factor that in its almost 60 wheel HP.

Whoever said you couldn't make this kind of power on the 4.3L was mistaken. I said it for years but nobody believed it... Now it's being proven true by many other as well.

Can't wait for stage 2 tune, then pulley, then headers + Stage 3 .

400whp should be easily attainable with all those mods, certainly no joke

 

400 whp would be a great target! I am curious to see what type of power the headers offer after all of this work. The stock headers aren't pretty, but they are a reasonable design for factory headers. Tubular, collected and divorced at the collector. I will be very interested to see what type of power they can manage. I would also be interested to see if increasing the volume of the intake manifold would help in the breathing of the engine. A phenolic spacer or something of that sort would be the simplest solution.

 

Eurocharged claims one of their customers made 19whp with just headers alone (no tune). That sounds about right given the stock headers are not terrible (although far from perfect).

Headers alone would put me above that mark, but I won't be doing those for a while. I will be focusing more on drivability and getting more of the existing power to the ground (pulley & rotors) along with special springs.

 

Awesome. Brilliant write up !!!!

 

Can anyone tell me where we can purchase wholesale Cats? We are a performance \ body shop in Florida and deal with a lot of high end vehicles. A customer just inquired about these cats for his Aston martin vantage 07. Thanks

 

Where are you located in florida?

The company that made these are in Orlando (Enjuku Racing) not sure if they offer wholesale.

There's also another company in Miami RSC Tuning that offers cats.

 

We are located in largo fl not far from orlando. Would you happen to have the companies info that distributes the high flow cats?

 

Great write-up, thanks for all the info and work you put into it!

 

Hi dralex,

We offer wholesale on all our products, and ship worldwide. Shoot me an email - Stuart@VelocityAP.com and I'd be happy to give you all the details.

Cheers,

Stuart