WELL FOLKS I DID THE PRE CAT REMOVAL YESTERDAY, LOOKS LIKE THE NUMBERS ARE PRETTY GOOD. AVERAGE 13.95@100.5 MPH 209WHP THE HIGHEST HP RECORDED WAS 211 WHP. I GUTTED THE PRE CAT AND THEN PUT IT BACK TOGETHER, I CAN SEE WHY THIS THING IS RESTICTIVE(SEE PIC BELOW) THIS STUFF IS LIKE ALUMINIUM FOIL AND VERY HARD TO REMOVE. NOT WHAT I WOULD EXPECT IN A CAT, HAD TO MACHINE IT OUT. NEXT IS TO ADD A STRAIGHT PIECE IN PLACE OF THE PRE CAT. THEN TEST AGAIN.
NEXT FOR SOME BAD NEWS, I THEN BUILT A 3" EXHAUST AND FOUND TO LOOSE ALOT OF POWER, THIS IS BACKING UP MAY THEORY THAT BIGGER IS NOT ALWAYS BETTER. 15.9@90MPH. I DID THESE TESTS AT 1:00AM AND NEED TO DO SOME MORE TESTING. BOTTOM LINE THE PRE CAT MOD IS VERY PROMISSING.

 

Im guessing this isnt street legal?

 

Yes It Is Legal, Only The Pre Cat Was Removed, The Actual Cat Is In Place.

Cheers

 

Sorry for the ignorance but what is the pre cat intended to do?
Mike

 

Cause Restriction, Ha. No, I Think It Has To Do With European Emissions. When The Car Is First Started It Runs Open Loop And I Think It Is Used To Filter The Exhaust While It Is Rich. I May Not Be 100% Correct On Its Complete Function, Be I Am Pretty Sure I Am On Track With This Statement. Maybe One Of Our European Friends Can Answer This Better

 

Excuse my ignorance, but what exactly is the delta of the removal of the precat? Do you have any idea what times or whp you were putting down before you removed the precat? This mod looks pretty promising and I'm seriously considering doing it.

 

Check The "son't Forget Your Head" Thread, I Posted My Numbers There.

Cheers

 

So the precat creates the following deltas:
quarter mile time: -.06 seconds
trap speed: -2.7MPH
whp: +4 whp

Is this good? The numbers seem to contradict themselves since it says you have more hp, but a lower trap speed... but I'm kind of confused by the results. Anybody?

 

Looking At The Rest Of The Times I See My 0-60 Time Was 6.45 After The Precat Removal, The 0-60 Time From My Other Post Was In The High 5's. There Are Many Varibles To Consider When Running A Distance Of A 1/4 Mile, This Morning I Went Out And Ran A 14.4 With A Trap Speed Of 105+, The Problem I Had During This Run Is I Had To Let Off Because Of Wheel Spin, In A Perfect Run I Think I Could Comfortably Get Into The 13's. This Thread Is In Response To The Pre Cat Thread I Started, I Will Be Testing This Mod For Awhile To Get More Accurate Numbers.

Cheers

 

I always thought that in drag racing, power (i.e. - torque/hp) were directly related to your trap speed regardless of your launch. That's why I wasn't really looking at the 0-60 or the quarter mile time, just the trap speed and hp. If you're running 105+ for trap speeds this morning, it would make a lot more sense regardless of your launch or times. Correct me if I'm wrong, which I probably am.

 

Pro Stock Car That Runs 7.0 In The Quarter Mile Sits On The Line, Light Turns Green And He Sits There For 10 Seconds Then Takes Off,
His Time 17 Seconds. This Does Not Reflect His Hp, Only His 1/4 Time, Hope This Makes Sense.

Cheers

 

Yea, I understand that. I'm not too sure if you're reading my posts, but I'm talking about your trap speed... not your times...

 

I Guess If I Was A Pro Drag Racer I Would Be Able To Duplicate My Times And Speeds, But I Am Not. The Only Way I Can Sum It Up Is Traction Is The Key, If I Was Driving A Car With A Auto Trans And Not Enough Power To Spin The Wheels, Everything Would Repeat Very Close. Again This Is Why I Will Do Many Runs So I Can Get A Good Average.

Cheers

 

Okay, okay... this is getting nasty. I apologize if I seemed a bit snippy. I had always seen on the RX-7 forums that they seemed to regard trap times as being directly correlated to whp and disregarded times since driver variation is too great. Anyways, I apologize if I seemed a bit rude.

Good job on the work. Do you happen to be running any ECU software? The Europe guys with MTH were claiming 10whp/15NM.

 

I Am Running Mth, The File I Am Running Is Not Taking The Header Mod Into Consideration. I Have A Request In To Volker To Send Me A New File. I Think This Will Get Optimum Power From This Mod. I Did'nt Think This Was Getting Nasty, That's The Problem With Commuting By Computer, I Hope You Did'nt Think I Was Being Rude, I Was Just Trying To Let You Understand What I Am Trying To Achieve.

Cheers

 

s'up with the creative caps?

 

Keep us updated on this. This may be my next mod, along with the HDI, MTH tuner, and M7 USS.... Wow, my fiance is going to kill me. Oh well, it's all for a good cause.

 

The pre-cat is for cold (Very cold) start emissions, as it light sooner (gasses are hotter as it's closer to the head). This will also help the light off of the main cat.

Any change to the emissions system isn't street legal, even if it makes the car cleaner (friggin stupid laws).

Getting repeatable times and powers is a major PITA! That's just the way it is with our cars....

With exhaust, it's about exhaust velocity. Too slow a gas speed, and scavaging suffers, and the individual pulses don't "pull" as much gas out of the cylinder, so bigger isn't always better!

That being said, if there's a big honkin' blockage in the exhaust flow, that's not good! This mod is an attempt to address that.

Matt

 

dr o,
you said it right. i did some more 1/4 runs today , this car is getting very respectable. the best was 13.5@108.4 0-60 5.25, the next was 13.9@103.8 0-60 5.65, the last was 14.00@102.8 0-60 5.67. having trouble with 3rd gear traction. i did have a crazy number that i don't believe yet, i will have to see it come out a few times to validate it, 12.9@131.6 0-60 5.17, i think this was a bad reading. i did add a 4% pulley and a 3" exhaust along with a mth file i have had for a couple of months. this is going to be my base numbers for testing of the header mod. volker will have me a new file to include the header mod in the next couple days. my first tests showed about 6whp with the pre cat mod, when i get the new file we will see how it affects these numbers, this should give a pretty good idea of what this mod will be worth in power. i know i am bouncing around with this, but i am trying to find the best all around combo for the least money. i will tell you now that the pre cat mod is well worth 1.5 hours of work considering the gains i am seeing. when i am done i will post a complete list of what i have done and how much i spent, remember i am still running the stock cam. before i started this project my best times were 14.65@96mph 0-60 5.85. quite a significant boost in prformance. bear with me, i will sort this out.

cheers

 

no it doesnt make sense
if u feel like cheating with some light systems u can actually reverse when the light turns green then have an extra 10 feet of runway to run ur time and MPH and u can astonish quite a few people
time ONLYstarts when u leave the line. so u can sit there for 5 mins if u want ur R/T time will just stink
ever wonder why pro drag cars stage MM by MM? Late staging

 

Looking better and better. Is the sound any different now than it was before? I'm worried about this since a lot of the header and exhausts are excessively loud and I'm trying to keep it as quiet as possible so if this alteration to the header puts down good power with no noise. It's at the top of the list since I want to get the Webb exhaust.

 

Really.

Makes it hard to take seriously

 

just out of curiosity... because i am unsure and i don't want to assume... are you getting these 1/4 mile times from a dyno?

 

*****, Any more pics? Picture of the header after the weld and before the installtion...

 

i started with a gt-1 made by passport, basicly a gtech copy. i will be the first to say the actual numbers may not be correct, but the differences in the numbers i believe to be true. i have not changed any parameters in the box since i started this test. the first time i had before any of the mods i have done was 14.65@96.7mph, this is with a 15% pully, cai, 2.5 dia exhaust. the best time i have had since adding the mods is13.50@108mph , i am running consistantly in the 13's according to the box. again not sure how accurate the box is. i will post the mods and increases i have seen from the beginning. as far as the header mod goes, i saw about a 4hp-6hp gain with out changing the ecu file, i am still waiting for the new file from mth. as far as the sound it may be alittle deeper but i don't notice it too be any louder.

cheers