Joe_G

This may prove an interesting debate. Let's see if folks agree with my conclusions.

I've been pondering my next mod for a while. I'm maxed on bolt-ons and cam, next mod is a FAST (or the new Weiand intake aka the ghost intake) or heads. I've been asking for some time for dyno files (.drf files) for a car with similar mods and a friendly forum member finally came through so I could do some head to head comparos using the free winpep software. Thanks to GTODoug for showing me how to do this.

His mods are: 2007 Z51 mz6, AR headers w/ cats, stock catback, ASP underdrive pulley, g5x3 on 114, stock head gaskets, ported FAST, stock gears.

My mods are: 2005 Z51 mz6, AR headers w/ cats, stock catback, ASP underdrive pulley, g5x3 on 114, Cutouts, Cometic .040 head gaskets and Ls2portworks intake, 3.90 gears.

Enough talk. What do they dyno graphs look like?



No, that's not the same car. But wow, those graphs are close. We were both surprised. My first blush conclusion based on above? I shouldn't waste $900+ on a FAST.

But let's dig a little deeper. Note our cars are the same except he's got a ported FAST, I've got thinner gaskets (thus more static compression, 11.44 vs 10.90) and I've got gears and cutouts. Common wisdom (based on my experience here on the board) would say he's got 15-20 rwtq/hp mid range due to FAST, offset by my 8-10 mid range due to compression, and my 6 across the board due to cutouts (that 6 is dyno tested and proven)...but he's got 5-10 more rwhp increasing as the rpm goes up due stock gears vs my 3.90's. I'm not seeing the last 5-10 he should have.

But as usual, the devil is in the details. And this should be a warning for dyno comparos...look at the AF range on the graph above. Looks close to the same, certainly close enough right?...but look at it when I make the AF range bigger and give you details on the exact AF at torque peak:



My guess (and I'd like those with more dyno experience than me to chime in) is that the additional point of fuel he has is costing him 20 rwhp/rwtq across the board. I say that figure as his AF ratio looks close to bone stock and most tuners move the AF ratio close to mine as the first thing they do on the dyno (which always gets a big smile from the guy who's car they are tuning).

So a more detailed review would lead me to a conclusion that a FAST will give me about 10-15 over my ported intake. I'm back to where I started...is that worth $900????

By they way, here's a dyno graph showing MPH vs RPM as the X-axis. Note how much HP for any particular MPH my 3.90 gears give me...that's why gears feel so much faster SOTP.



I'd appreciate comments from those more experienced than me to challenge my reasoning or conclusions drawn herein. I'd also like to hear from experienced tuners on the effect of the AF ratio on dyno numbers. And everyone should be aware of the effect AF ratio has on dyno power...my guess is I could have leaned my car out and got another 5-10...but I didn't want to risk it.

Joe_G

By the way here's my car cutouts open and closed. That's the only difference in these runs.

LSCHLEM

Joe Im not an expert tuner but an a/f of 11.83 is way too rich. You make an interesting point about the bump in CR. Put on a ported fast and you will have about 20 more especially in the midband.

Finster07

Excellent post.

You technical questions are out of my league, but I do have a comment on my FAST.

You asked if a FAST is worth the money for 10-15hp. Not only did my ported FAST deliver in the hp/tq and SOTP department but it delivers in the looks department as well. I had my FAST professionaly sanded, painted gloss black, and clear coated, along with the porting and modifying. That unit looks awesome and is the center piece of my engine compartment. Everytime I lift my hood, that clear coated FAST just stands out. It was certainly worth the $ for me. I'll admit that it was more than $900 by the time I was done. No regrets here.

I like your graph and explaination of how your 3.90's increase SOTP acceleration. That confirms my decision to get 4.10's for my in town daily driver.

Black02SS

Few things I've noticed when doing cars is that depending on the dyno, there is a difference from wideband's being placed in the tailpipe compared to the headers. I have seen anywhere from two tenths to a full point out.

If we conclude that the tune is correct and the only difference is "mechanical", then it shows how a few changes can impact how a car reacts. My opinion is you would gain more with the FAST due to the smaller gaskets. I feel it would just escalate the graph that much more.

Craigster05

I still say come to NY, have some fun at Carlisle and take my car for a ride.

0C_Williams@RPM

Flow test the FAST vs a ported LS2 and you will see the gains are going to be substantial- even better if the FAST is properly ported.

Charlie

Joe_G

I'm quite sure one ride in your car and my next call is for a set of L92's!

I'm worried we'd have to flycut my pistons so deep to make those heads work with my cam that it wouldn't be safe. And I don't want the hassle of changing the cam. I helped a buddy swap heads the other day, that's not such a bad job. But I don't plan to swap cams in this engine again.

Maybe someone will chime in with details on how deep we'd need to cut.

Charlie thanks again for your mail order tune. My car drives like a dream for over a year now in daily stop and go traffic.

AintQik

Joe, there are too many variables between dynos, dyno days, operators to get a fair estimate. For price I'm a big fan of Spin's set up. Can't beat it. Even buying a new cam, once you sell off your old stuff the cost is negligible.

I feel the FAST will out perform an LS2. If its worth $900 I dunno. Don't forget you need to include the cost of porting, modification to either the manifold or the car, fuel rails etc. It's going to climb higgher then $900. I ran one up until I went FI and the guy that has mine is making 20-30rwhp over stock (unported stock) with a nice curve.

Plus as Fin mentioned it does look pretty cool sitting there. Go to a local gathering and open the hood and a pretty FAST gets the wow factor.

If it were me on a stock bottom end car I'd do Spin's set up and put down 480.

A-Pex

Being "the guy" that has RJ's old FAST, I can corroberate his assessment of the HP/TQ increases on my 06 A6 (350/349 as it sits).

That being said, according to Spin's review of my dyno sheet, the TQM is pulling timing above 5K and I'm currently leaving anywhere between 10 and 20HP on the table (we'll just have to see what it looks like after Spin finishes the tune).

So, a conservative estimate should result in a 30 to 40 rwhp increase and potentially as much as a 40-50 rwhp increase, though I'm guessing closer to the conservative 30-40 estimate. That's with a "ported FAST" only.

Side Note: LPE CAI did not result in any noticable gains on the dyno

I'll post the dyno sheets on this thread when it's all said and done:
http://forums.corvetteforum.com/show....php?t=2091613



~Lou~

The Clevite Kid

Thanx, Joe, I did not know that gaskets alone could raise compression by 1/2 a point. What is the rule of thumb on the LS2 for how much lowering of the cylinder head (by thinner gaskets or by milling the head deck) is needed for each 0.1 gain in static compression ratio?

I see a number of tuners (like Cartek) including a milling cut of 0.030 on there tweaked 243 heads.

Mike V.

Joe,

You know where I stand here. We have similiar set ups right & my cam is 230/232 int.598-exh.603 114LSA. I would guess, what you make w/ compression bump is lost on the dyno w/ gears. That said, given a fairly mild cam I made 452/418 (468/433 corrected) & I'm betting it's the ported FAST that gave me the , lets say, better than average numbers. Interestly enough, both Guy & my tuner predicted 436, I don't know if Guy new I was porting the FAST & he probably was unsure of my ability, 'cuz he actually did the firewall portion to save time from all my questions (Lol), & my tuner didn't give it any weight. So my conclusion is the FAST, ported in particular, is the way to go!

Mike V.

Joe_G

Clevitekid, there are spreadsheets floating around to give you the answers you seek, seems like I has one from ls1tech, I can't link from my iphone but you could search if you are interested. If you have no luck let me know and I'll get in my computer for you and send one to you.

Mike those are some super stout numbers. If I could spend $900 (or less if I can buy a buddy's LOL) I'd do a fast. Could you post up that dymonsheet or forward me the .drf file?

LSCHLEM

Joe, you can be right there with the PORTED FAST Meaning ypur numbers will get to the 450" HP/ 430/ TQ I feel so confident of that. I wish there was a way you can try the FAST. Your welcome to try mine
when my car is at Chucks for a CAM & HEADS. If I go L92 the FAST will be yours for a tremendous deal. Why dont you take a couple of days and come up to Carlisle. Ill be hooking up with Craigster, Chuck & Cameron.
Its going to be crazy. We will have all kinds of fun. Leon

keyplyr

Aside from porting and the installation modifications, I chose to leave the appearance alone. It looks like a FAST intake manifold, go figure. But then I also got rid of those useless FRCs that hold in all that heat.

I don't belong to that club of old men that stands around looking under each others hoods in some parking lot. I'd rather be driving.

BOB EAGAN

I think what color you want is your choice. I also think your second statement was rude. I personally don't do the parking lot thing either, but for some people, thats what floats thier boat. They are Corvette owners and forum members. Don't know how old you are but before you know it, you'll be an old man too.

Joe_G

Man Leon I would love it!! I'm so busy with work now though. It's not gonna happen. I'm hopng to hook up with Cragister and Spin in Vegas for SEMA though, maybe you could make it out there....

Appreciate the offer, very kind of you. If I haven't bitten the bullet and gone L92 myself, I'll take you up on it. I think if someone knowledgeable chimes in and lets me know my pistons will take the cut, I'll just put on the heads and be done with it.

keyplyr

60 and I guess someday I will be old. What does that have to do with anything? I still don't stand around looking under everyone's hood. I could care less what things look like on the engine. For me it's about the engine's performance not how shiny the plastic parts are, and BTW any statement I make pertains to me and me alone so nothing I said above is rude.

Enjoy your car.

bunk22

Always good deals out there Joe. I paid $700 for my FAST and all parts. It was a new FAST, never been used but the seller wanted to get rid of it. Saw a few for $500-600 used but I was to slow to ****** them up.

5abivt

How do the both cars run side by side ?

I would not suggest leaning out the rich car. Remember this is a dynojet and there is not 'real' load on the car. This is why to some degree Mustang dynos are more accurate than dynojets. you can lean it out and pick up some hp on the dyno but on the road it could be costing you power. A car that is tuned right on the road will show to be running 'richer' on a dynojet.

A more accurate reading of A/F would be to have widebands in each collector positioned optimally and the car on the open road under load.