I am posting this to provide insight into what mods can achieve on this car. All work was done by Orange County Corvettes.

All dyno numbers are Dynojet 248C, SAE corrected. Runs took place under similar weather conditions (mid 70s, humid beach weather), and on the same tank of 91 pump gas from Arco.

Car had 13,500 miles consisting of mostly interstate highway, with an estimated 2,000 of very hard near-the-limit canyon driving. I am well past 1/2 on the second tire set.

354RWHP bone stock. AF was susprisingly good, with some leanness in the midrange, but pretty much 12.5 all the way thru redline. Typical slight trough from 5800 up probably indicating onset of valve float.

360RWHP with 5mn of minor teaks to correct a couple of trouble spots.

403RWHP after installing:
- Kooks 1.75 LT with cats and 4 O2 extensions, stock mufflers
- FAST90 with at least 5 hours of clean-up work by me. Yes, that's right. And that's with me being very fast with a rotary sander due to having a lot of woodworking experience. The plenum area is good to go, but a lot of dremel work was needed to adress impediments to airflow about 1 inch in from the port area where the 3 pieces mate up. A lot of this is perplexing and could have been adressed via better casting detail. Initial material removal was via 60 Gr sanding drum or rasp for tight corners, and finish work by hand with 220 paper. Note I did not increase port size.

- ported stock TB (Sean spent a good 3 hours on this, this is a very rough piece stock)
- Maf screen delete
- Vortex ( took 3 hours to install this due to poor fitment of pieces. I cannot recommend this product for the C6 due to that, even though the C5 product was great)
- 1.85 Comp Shaft Roller Rockers with Patriot Dual Gold Springs, hardened pushrods, and Ti retainers. Note these are not the SLP, non-roller units.
****No tuning had been done at this point.****

378RWHP after installing 4.10 gears. We were surprised by the 25HP loss from these, but this probably reflects the gearset not being broken in at this point, so things are still pretty tight. Still no tune.

400RWHP on the nose after full tune by Sean. This was not a full SD tune, but Sean worked on the car for about 4 hours making adjustments. More impressive than the 22 peak increase was the big bump in midrange power and the elimination of the 5800+ slump. Sean indicated he actually did more power than this but decided to keep it conservative given the car goes to places like Utah where gas sucks.

This means the car would have done 425-429 RWHP on 3.42s with the above mods on 91 oct. gas. This is a damned impressive result, and I think it reflects the importance of not only getting the FAST90, but of doing the work to it to maximize its potential, as well as adressing every detail of upstream flow such as the TB porting. And let's not forget the importance of a great tune.

I have not gotten on the car yet because i have 300 miules of mandatory breakin to go on the diff and valvetrain, but it sounds great. After break-in, it goes back to OCC for a final tune (LT trims) and dyno run.

Some comments:

headers + stock catbacks are great: near stock at idle and around town, with zero drone, but with a roar when you get on it.

the car went in with horrible clutch chatter and I had requested a new clutch under warranty, imagining the disc was shot and the pressure plate burned. Sean changed to a C5 spring and replaced the fluid, and the clutch feels totally fine, as new!!!! Go figure.

This car was running extremely well from the getgo, with spot-on trims. I suspect cars with 345 HP are simply not as well tuned from the factory, so that is why you see some cars getting monster gains from headers+CAI+tune.

The tune is worth it for feel alone. The engine felt mushy before. Now it has razor-sharp throttle response and much more power, even at part throttle. The car now has that same mojo I loved in my C5 Z06.

Sean and his crew are top-notch. The work was well done, the car was impeccable inside and out when I got it back, and they really took the time to do things right. They are very busy, so book in advance.

And no small thanks goes to Spinmonster, who persuaded me to go the headers and FAST route, even though these are mods I famously ridiculed on many occasions. This stuff really works, and it works even better together. Thanks also to Spin for making me realize that this type of approach lays a solid foundation for cam and heads later on.

One final note: Nitto R2's on an extra wheelset will be part of the total traction package to handle the 4.10s and the added power.

 

Concur on this..........Sean and his shop are awesome. Great experience with those guys. Good write-up as well.

 

Well, excellent results. Are you running cats on the car? I contemplated going the very same direction. However, I decided to run a ported stocker(manifold) and a cam. The FAST always needed cleaning up. I have had AFR port my FAST on my 408ci gto and it sent my FT's lean 3-5% everywhere.....a good sign. After tuning the porting was worth roughly 15whp on the 408ci block.

I decided to go with the cam as opposed to the rockers. After figuring the rocker kit was going to cost me roughly 1000 bucks plus 200-350 in installation, the cam ended up costing me 800(cam kit) plus 800 installation. It was too close in cost for me to be able to justify the additional hp I'd leave on the table. However, the beauty of the rockers is no loss in driveability and awesome power under the curve. The cam is a compromise in driveability and a shift in power under the curve.

Please post the graph with the results. I got 390whp with the same mods minus the FAST and rockers on stock gears.
Ported stock manifold
LT headers
catted 2.5" x pipe
Ported TB
Vararam Intake/Spacer

The car got dropped off for the cam install today so we'll see how she does.

Great write up with even better results.

Dougie

 

Very nice gains!

Take out the 4.10 gears and that would suggest your car is making 425rwhp with stock gears after the tune.

That is Z06 territory.

Then again, I never can tell #s from dyno to dyno and from dyno #s to track #s.

My car on stock tune with Corsa Sports and K&N aircharger ran 12.55@115.85. It probably dyno'd in the 340-350rwhp range.

After headers, stat, and a tune it dyno'd 370rwhp/375rwtq SAE and ran a best of 12.66@114.75. I was not happy regardless of dyno #s.
After a second tune to tweak the car and many passes it ran 12.61@116.02, a whopping 0.17mph more than before the headers and tune.

Then I went to a new shop where the old 370/375 = 381/399 on their dyno.
After a 3rd tune it makes 395/402, but unless it traps 117+ I could care less about my dyno #s at this point.

Are you gonna get the Nitto R2s before you hit the track???

My experience with R compound tires at the dragstrip has been very positive.
My 2001 Viper GTS ran 12.35@118.52 on a 1.89 60', with only a simple swap to Kumho Ecsta V700 R-compounds, it ran 11.67@120.56 on a 1.68 60'.
Even launching conservatively on the R-compounds it never ran worse than 11.8s and 11.9s@120+ on 1.8 60's.

Good luck and enjoy the power,

Howard

 

gtodoug: yes, that is with cats. Several years ago, I got to see a random technology cat flow-benched against a straight pipe - there was zero difference at 1200 CFM, so I think minimal loss would occur there.

I initially was going to do H+C and forget all the other bolt-on stuff (the headers, mostly), with 4.10s. I decided that H&C had to go together so you set up your heads according to the DCR the cam you choose will provide. Mostly, I did not want an agressive combo I would not like later and I did not want to have to redo stuff. And I wanted to keep that fat stock torque curve and was insistent on that point. So I decided it was best to start with a solid foundation for more power later if I want it. Stable valvetrain, good breathing in and out, good tune and street manners. I will drive it for a while and see if it is enough power. If not, then I am all set for H&C.

Yello3 The Nittos are intended for the street and the curves. Honestly, I do not see myself going to the strip with this because I am a lousy dragger and will definitely break something...I just know it. I know I should, but...

I totally agree with you that the dyno numbers themselves are meaningless. What is important is what the gains were. In my case, that was roughly 65HP from this set of mods, which is very solid. This began as a budget tune, but it really became an exercise for me and for Sean to see how much benefit comes from improving airflow to the stock heads. I think the work he and I did to the FAST and TB were worth 15-20 HP in and of themselves at this power level, which is a nice gain and definitely worth the effort.

I really wanted an engine that will deliver smooth and responsive power on the street and that I can run at high RPM all day long if i want to with no worries. Time will tell, but hopefully that is what I have here.

Eventually, I would be curious to compare mine to a H&C car without all the airflow

 

Terrific results

 

@ Yell03 - what was the new shop? The first one didn't get the job done to your satifaction?

 

I'll PM you the new shop.

They are not a supporting Vendor, YET, but I am working on it.

Howard

 

Nice, detailed write up!

I think we can really see where you're getting all this power from, though.

 

[QUOTE=yell03]I'll PM you the new shop.

They are not a supporting Vendor, YET, but I am working on it.


I see your point.. we mod for performance while driving not for the dyno. I would be extremely disapointed with the 1/4 mile performance after the mods.
I wonder if you might have cut a better E.T. with the headers.....prior to the tune??

 

Cookee -

The new tuner did just that, he plugged in all the values of a stock tune and power immediately jumped up.

Then he tweaked some variables so the car would not pull timing, played with the a/f's to keep them at optimum, and we gained 14rwhp.

So, basically I have an upgraded stock tune,

Howard

 

Yeah, I know. I should be taken out back and shot.

Actually, I did this on purpose. I have seen some really bad gas during my roadtrip adventures...

 

Marc...nice writeup, I'm very happy to hear your results.

 

Thanks Richard. Did you get your car back with the APS in it? Give us all a quick review of it...I'm sure it's incredible.

I cheated a bit and jumped on the gas today. What an incredible sound from those headers and the higher lift !!!

I'll say this, anyone hesitating to do headers + stock rear exhaust...wait no further. Even if there was zero added power, it would be the ideal exhaust mod. Stock quiet when cruising, zero dron at any speed, but then you get this amazing sound at WOT that is part big-block and part Ferrari.

 

Marc, not yet but I expect to take deilvery sometime this week. The hardware is in, the motor needs to be heat cycled and finally tuned. I do hope to get the pleasure of meeting you at one of these Corvette gatherings soon...let's keep in touch.

Have fun with your new mods and be safe.

 

Richard, your engine and twin turbos should be a very nice combination when run in and tuned, will be great to hear back from you in the near future.

Peter

 

Thank you Peter for your continous support, the perks of being an APS customer is

We were heat cycling the motor this evening as you can see the vaccum pressure & rpm on the EBC:

 

I definitely want a ride!!!

Finished break-in and had a chance to really get into the throttle. Man does this thing pull hard. Sounds freakin' awesome and all the torque and more is still there with great top end. I'm lovin' it. This engine really responds to mods and tuning.

 

Hi Richard, My pleasure to do so and I'm really excited and can't wait to see your C6 402 cube twin turbo beast completed. If I ever get over to LA in the near future I'd love to have a blast in the C6, that would be awesome, just insane.

I know that the LAPD guys have been working overtime to get this project completed and I'm sure thet they will be thrilled and very proud of their input to your C6 so a big thumbs up to the LAPD guys.

Peter