Not much going on in "performance section", so I figured I'd post here as well for those curious.

I couldn't justify the price of a FAST 102 so I tried the Dorman LS2 intake at half the price knowing it will need some massaging as it's not perfect. Shown below is the process I went through to "port" it which was spent reshaping the runners. I did not touch the actual port size since my heads were stock, the ports match the heads already.

The car:
03 Z06 60k mi
BTR Stage 2 cam
Stock LS3 air bridge + card MAF on SD tune
Mamo ported LS2 TB
Dorman LS2 intake
TPS 1 7/8" headers, catted X pipe and Corsa Sport CB


Cliff notes on porting a DLS2 to a stock 243 heads:
1) DLS2 port width at the head matches that of the stock heads = not worth widening to the reported 1.1"
I had access to PORTED 243's with a port matched FAST 102 to those exact heads which DID show 1.1" head/intake port width AND that the intake porting was "angled".
2) The runner thickness at the area that needs the most removed is ~5mm. (drilled a hole and verified thickness at each runner).
3) The runners of the DLS2 and Fast102 look very similar in design/shape but the FAST has a substantial larger plenum volume (obviously hence the increased height which may allow slightly longer runners)
4) It seems like one engineer designed the upper runner half and someone else designed the lower flange half then glued them together...fairly poor transition between the two halves.
5) All said and done there was more material on the floor than I ever thought.

Ported FAST102 lower section on stock 243 heads (I borrowed this FAST to take some porting pointers)

Drilled a hole in all runners where most material will be removed to check wall thickness

The hole ends up directly in the corner of the runner

Put drill bit back in and verified wall thickness

Final product. Removing this much material you need to be careful. The wall can get paper thin to where light will shine through the plastic. I worked my way "UP" the runner focusing on blending the large runner radius to the smaller port radius. If you wanted to go nuts and make it perfect you could also fill in some low areas but what I did was 90% there that I didn't feel the need to spend a lot more time on this. I did NOT touch the original port opening here as I felt it lined up well on stock heads. More porting may be needed once heads get ported.

Here you can see I got too carried away on this one as it was my first one...lesson learned. This shows aluminum foil tape inside the runner as a backer to keep JB weld from dropping through. I also sanded then "hatched" around all holes to let JB weld bite. Once JB weld was solid enough but still pliable, I removed the tape and smeared more JB weld over the small holes and let it fully cure.

Not pretty but functional. I'll address aesthetics later.


Results below are the following (bold are the incremental changes) pulls done starting 2000rpm in 4th:
Blue = Halltech "Stinger" CAI (filter placed behind filler plate), stock C5Z MAF, Mamo Ported LS2 TB, untouched Dorman LS2 intake 381/334
Green = Stock LS3 air bridge + stock card MAF + SD tune, Mamo Ported LS2 TB, untouched Dorman LS2 intake 385/338
Red = Stock LS3 air bridge + stock card MAF + SD tune, Mamo Ported LS2 TB, ported Dorman LS2 intake 393/344

*Blue and Green pulls done on same day and same dyno back to back swapping CAI (Nov last year). Red pull was done on the same dyno this past Saturday.

I liked that the TQ curve is not just a peak gain but a gain across the whole pull. HP starts to gain around 4200rpm.


Resulting A/F graph. Since this graph we added some fuel up top to make it safer with no loss in power (dyno above are after fuel adjustments)

Porting the Dorman was worth 11hp/6tq. Just reporting my findings. I'd be curious to bolt a FAST102 on and see if there is much more to be gained. At the time FAST102 was and still is ~$900+. The DLS2 was $410 shipped. I believe I make at least 80% of what the FAST would give me with my combo. So I don't see a huge benefit to seek a FAST102 given the cost and I don't have any fitment issues or the need to shim the cradle/lower motor mounts.

 

Excellent write-up. Thanks!

 

Nice data. I've been eyeballing the Dorman LS2 as well... just not sure it's worth that much cash for a few extra ponies for my daily driver.

 

Well they can be had for the price of a OEM LS6 intake. Benefit is you can move to a LS2 TB at the same time. The LS6 will need the TPiS 90mm mod and in the end you spend more on the modified LS6 90mm intake than you do on the Dorman LS2 unit.

I would have gone with a used FAST 102 if they were selling for $500 ish. But used are still $700-800.

 

Yeah my '02 already has an LS6 intake, so it's really a tossup for me. I want to do something else, but just don't know if I can justify it.

I've been looking at cylinder heads too. That's probably the next thing I'll really do.

 

I think the Dorman LS2 is slightly better than the LS6 but that could simply be from additonal plenum volume and larger inlet of 90mm. But like you said, can you justify the cost. Once you go with the DLS2 you are locked into finding a 90mm TB which for used SILVER blade units is around $250+. So back that into your budget.

You can sell the LS6 and get the DLS2 + ~$100 and then add another ~$250 for LS2 TB. The DLS2 and LS2 TB will be a good addition to heads later on.

 

Bump for posterity, I'm definitely saving this as I've got a DLS2 on the shelf waiting for some grinder love.

Thanks for sharing and posting this in a few places! We need more solid info on these manifolds.

 

No problem. I like doing stuff like this, I just need to remember that if I'm doing a project to post somewhere I need to take strategic pictures. Otherwise I just chug away lol.

I'm fortunate to have a friend that owns a speed shop, so getting on the dyno/tuning is "free" (aside from buying him lunches and manual labor around the shop with stuff). So being able to back to back testing is key.

I started this post for LS1Tech due to finding a guy that did personal flow bench testing of MANY intake manifolds on his own time and own dime. So I tried to offer something useful to that thread given my resources and access to a dyno. I then copied and pasted it in here for anyone curious. LS1Tech has more posters interested in this DIY/technical stuff where CF seem more interested in "engine dress up kits" and "best exhaust" (with exception of racing sections here). Just a different culture that's all.

IMO for the money (keep in mind I came from a LT1 Fbody and LS1Tech mentality, so putting in effort to make something work like porting this intake was fine with me) the DLS2 is worth it to step up to a LS2 TB and then even more so after porting as you can see here. Where most on CF may have the coin to jump right to a FAST102. Which is fine since I think that's THE answer and end all be all intake right out of the box. There have been MANY videos and test results from Rich Holdener doing intake manifold comparisons and in the "long runner" designs, the FAST102 wins...but at a $900+ price tag. I picked up the DLS2 for $410 and after a Saturday of porting I believe I'm 80%-90% of what a non-ported FAST102 would be out of the box on my car. I would love to test a FAST102 to see what gains there would be left, but I don't have one and it's not a simple bolt on since the cradle needs shimmed down etc to make it fit.

 

Update: Running the same setup and no issues at all. No signs of JB weld failing. The car has been through ~3 autocross seasons.

 

Nice! I ended up picking up a FAST92 for cheap ($400, because the guy painted it and it was ugly).

Still haven't put it on though... lol

 

this is great data, today the Dorman is priced up there with the FAST

 

Yup, at which point I'd do FAST if I was doing this project now.