bogor

Yesterday, I tried my luck against my friends stock 2009 ZR1. We made a couple of runs, from a rolling start (on a closed circuit of course) from 45-50 mph (3rd gear about 2500rpms) to about 120 mph. Result; he pulled away from me from start until we shut off (not “darting away” but he was clearly faster). Even though its prob not possible to close the gap, I would at least like to narrow it a little. I am at about 530RWHP (http://forums.corvetteforum.com/c4-f...-trim-etc.html) and the question is what to do next? A bigger blower head unit? Considering the fact that the Mustang guys seems to reach 600RWHP with a similar S-trim blower I´m not sure this is the answer.
Maybe a new intake manifold (almost stock Superram and edelbrock base now) as suggested in my old thread? My boost peak around 13,2 psi and I think this indicate an intake restriction. A guy here reached 732 RWHP from an LS engine and a Vortech Si trim blower and max boost only 8.7 psi with an Edelbrock Pro-flo XT ram intake. After reading this http://www.camaroz28.com/forums/forc...esults-721895/ I purchased an Edelbrock Victor EFI single plane intake. I am however somewhat reluctant doing the swap since it involves quite a lot of work (getting old and lazy I guess) so I wanted to get some input before starting to tearthings down again.

drive it

Have you put it on a dyno and tuned the wot fa with a wideband?

mnstrlt1

The ZR1 has a different blower (positive displacement). The power is instant, and it holds. These centrifugal blowers build power in a linear fashion. The reason i am pointing this out is because a bigger head unit or different intake will yield more power, but will magnify that initial jump he gets on you. This is because the power band will be shifted up more (with either modification), "but" you should be able to close that gap and "possibly" gain on him.

Keep in mind, these c6's also plant the power better.

*also, I've chatted with Gregg several times, and I've now had 2 T-trim blown c4's, the head unit just runs out of steam on our platform at "about" 550-600rwhp. Any more, and the dyno is being generous.

Mustang guys can run a lot larger crank pulley, and they might also be spinning the engine higher (more RPM's).

bogor

Yes and yes.

Just returned from the track and the result was mixed. Since my last attempt on the quartermile resulted in two broken driveshafts I was VERY gentle when taking off (running ET Streets). The 60 ft time was lousy (like 2.1-2.3 sec) and the best ET only 12.6s. However, the trap speed was better than previous times at the track (the best run today was 120.0 mph). The AFR was about 11.8 and I also tried various ignition advance settings without any significant improvement.

I dont get it why the C4 platform and the old gen SBC should be a lot worse than the LS engine or Mustangs when it comes to a boosted setup. If you can spin the blower to max speed without slip and use good flowing aftermarket parts on both intake and exhaust side-there should not be that much difference in output..maybe missed something..?

After seeing what can be achieved by an S-trim on various non-C4´s I think I would now go for a better flowing intake before upgrading the blower.

BlowerWorks

Well I am no expert but the LS style engines 'breathe' so much better. With 5 pounds of boost we made over 500 RWHP on a 1999 C5. I was amazed to say the least. GM did their homework. The traditional SBC just cannot compete. Oh yeah you can do this and that (like a YSi or a F1) and get there but just think about it - obviously the thermodynamics of the LS are just superior to the old SBC - period !!!!!!
greg

bogor

My AFR heads flow about 300cfm (the LS1 heads flow around 250cfm). My idea was to get an intake that match the flow of my heads (my current Edelbrock + SR seems to be around 240 cfm) and this would get me close(r) to the breathing capacity e.g. of a LS 1.

HighMileage

Bogor,

I mentioned this in an earlier thread. With your heads and exhaust, the super ram is leaving a lot of top end power on the table.

Your best bet would be a tpis mini ram, its torque curve at upper rpm should net you at least 50 crank horsepower. The super ram, while being better than the long tube TPI, still rolls off torque at upper rpm.

If your redline is 6k a mini ram will make more power and should breathe out to 6500 pr 7000, if you go that high.

If you have 6 speed a mini ram will also better match your ratio splits on the shift. Lingenfelter did the super ram to match the 700r4 ratios so you would drop into the torque peak at the shift at the expense of upper rpm breathing.

bogor

Yes, I recall your advice and I actually got the Victor Efi single plane that possibly is an even a better highrevving intake than the MR. I will now start to collect the rest of the parts necessary for the swap. I got a 6-speed and this intake might get me a little closer to the ZR1.i will wait looking into a larger blower until I have gotten the results of switching intakes.

mnstrlt1

You might need this intake elbow to get your combination to work without too much fuss;

http://nitrousoutlet.com/lt1-boosted-intake-elbow.html

bogor

Thanks, that is one option if I would like to to keep the stock like TB.

I am actually thinking about this http://www.superiorairflow.com/carb-...-carb-hat.html and a 4 barrel TB like this one http://www.ebay.com/itm/FAST-High-Fl...-/190855978318

mnstrlt1

Both of those will also work, just a matter of altering and adjusting everything else to also work with it. I like the idea of a single plane intake manifold for "ultimate" power, but I tend to avoid too much custom fabrication/alteration or additional cost (try to use what you already have- throttle body). Either way, I'm excited to see the end result.

lcvette

You are going to probably want a better suited cam and valvetrain to work with your 300cfm heads and single plane intake manifold.. as Gregg said hard to compete against the LS architecture but if you want to get the most out of your setup, a single plane and big heads with a smaller cam is going to be better but not maximized. maybe give it a try and if you want more you will always have the cam upgrade to fall back on. just remember the valvetrain, big difference between 6k rpm and 7k rpm as far as what will stay reliable, better springs for the additional boost and strong push rods for the stronger springs and good rocker arms for stability and minimal deflection and weight, it all snowballs..lol

Chris

bogor

Thank you Chris,
Haven't really thought about the cam. Since I need to pass emission testing I am somewhat limited in how much cam I can use. Today its a HR with 224/234 and 114 degree LSA and 0.568/0.571 (int/ex). I have comp cams Hitech pushrods, promagnum steel roller rockers and the HD AFR springs (8019) so I think it should be possible to spin it pretty high (at least higher than the 6k I stop at today). I agree, if the intake won't give me the expected outcome a new camshaft might be the next step.

lcvette

I think the intake will make a wonderful improvement, they have even shown to produce more power with no torque loss over the lt4 intake manifold. that cam sounds fairly healthy for a street car you will likely see some very nice gains. also remember the higher she spins the more boost she'll make so there will be your biggest benefit to the single plane intake manifold... broader torque curve for better acceleration in each gear!

Chris

mnstrlt1

Chris-

Keep in mind, with the "cap" on the crank pulley diameter, and dependent on the head unit pulley; the blower does have a ceiling on impeller speed.

lcvette

true.. better make sure you aren't over spinning they blower with your new found rpm... however I think you will still be safe with that head unit... maybe a call to vortec just to double check.

bogor

I am overspinning the blower if I exceed 5800 rpms (and I do ) with my current pulley combination. I am using the stock 7.2 " crank pulley and a 3" on the blower (Gregs slotted one)and no sign of belt slip and raising the max rpm with a new intake will prob require a larger blower pulley thus no issue spinning the blower to the max (no need to increase crank pulley diameter).

mnstrlt1

Increasing the crank pulley would further "over-spin" the blower. Going to a smaller head-unit pulley will "slow" it down (which is what you'll need to do when increasing the engine speed, in order to stay within the blowers limits).

bogor

A smaller blower pulley will make the blower spin faster (with the same crank pulley size).

Anyway, I think I will rotate the elbow 90 degrees to eliminate some bends and pipes.


To be continued...

lcvette

that sharp 90* right on the blower outlet is a killer, I would cut that off and straighten that out as your starting point.. looks like (1) 45deg bend would be ALL required to hit the new TB location. Are you planning on keeping with a conventional style TB or single bore or carb style 4 barrel TB? converting to an LS style 102mm TB would be the easiest I would think they have provisions for the GM TPS and IAC valve built in and will flow a lot more then a dual bore twin plate throttle body.

just brain storming with ya... I believe I will be using the 102mm ls style TB such as this one..: