Midpipe, Before and After
 

About a month or two ago I put a catless midpipe on my car as opposed to running the previous stock cat. I had the chance to have my car on the dyno before and after so I have a boost plot.

My car is running the stock twins in parellel, With the midpipe i did pick up alot of spool time, and the car seems to be making a little more horses everywhere, however im not getting boost creep like everyone says i should be? am i just lucky?

(main point of this post is to give people a real graph of boost before and after a midpipe on the stock twins)

catless is red, stock cat is purple

https://www.rx7club.com/attachment.p...postid=2429599

i think you would only get a creep with midpipe if you were running stock sequential system, But i'm not 100% sure though.

Looks good by the way

No, thats not true. You can get creep with non-seq as well. Past 4,500 RPM the two types (seq and non-seq) operate exactly the same way.

Every car reacts differently. It depends on a multitude of factors. What are your other (relevant) mods?

Rob

apexi twin intake
jdm downpipe 3" ?
apexi n1 muffler 3"
catless midpipe 3"
haltech e6k
rikki non sequential

bov's shifternobs and break pads :D

Soem people creep some don't. When I was going to put my midpipe on I was ready with a restrictor plate and everything, but I never got creep, so I never put on the restrictor plate.

so what was your RWHP? I would like to know. Chart looks good by the way.

same two runs, colors coiencide

(I tune the car myself)
https://www.rx7club.com/attachment.p...postid=2429807

How stinky is it on cold starts? driving? People behind you changing lanes to get away from you?

It looks like you have the opposite of creep?

Its not bad for smell, (i idle my car around 13:1 afr)

but it is a bitch to start now that its cold out, usually takes 2-3 trys. Im hoping to try and tune that out when i get the chance

I'm no expert but your numbers seem a little low, how is your A:F?

af runs about 10.5:0 - 11:1, running about 19 degrees of timing.

Its possible that my second turbo is shot, i went non seq because i couldent get over 7 psi on the secondary. Ive got a single on the way to me right now so i can be done with the twins. Either way its still running the stock intercooler, so i dont think the numbers are too low?

Boost creep has nothing to do with having a midpipe/cat. Your catback is the final restriction in your exhaust system and what would more likely deteremine creep. I have a highflow cat and a midpipe. I dont have any boost creep with either. I spike with both though.

I have had 2 sets of turbos and neither one have boost creep. I even put a straight through exhuast and no boost creep. My tests were all done on the 1/4 mile track at Sears Point.

David.

When I had similar mods, the main cat, and stock IC seq. (12-13psi) I was putting down 300wrhp. roughly 40hp diff? Maybe that's the reason for the drop in boost...bad secondary. GO GET'EM SINGLE!!!!

.....

Also thats a dyna-pac which will report #'s about 15 pct less than a dyno jet. On a Dyno-Jet you would have been around 297 RWHP.

40 hp diff? are you lookin at the torque graph? i put down 293 :D

My bad man, I was looking at the hp @ 6462 rpms

I'm an idiot...the pic was too big for me to take in all at once ;)

nice #'s

that 293 was flywheel HP. on a dyno jet you would put about 297 to the wheels.

no, its whp... I dont know why our dyno says that, the only way to get flywheel hp is to measure it at the flywheel. This is actual whp

edit: i just asked my boss why it says flywheel... its cause we can put a tcf value in to correct it to show flywheel hp... but in the case of my car you can plainly see that the tcf (lower right corner) is set to 1.00 which means that it is not using any flywheel correction factor and that is true whp

IC, well the type of dyno you were on was a dyna-pac. As I said earlier a dyna-pac under-reports your hp as it was designed for AWD (its very good for tuning). If you would dyno on a dyno jet your #'s will be around 335. I dynoed at 316 on my previous engine with a MP @ 12 psi.

very good #s anyway.

Whatever the last component you upgrade in your exhause is going to be the one that determins creep (and the size of your wastegate) so if the last part to be upgraded is the stock cat; then that would determine creep.

not true. If your cat back exhaust is restricted you will not get creep. I have an rx7fashion exhaust which is an HKS. I upgraded my highflow cat to a midpipe, no creep.

You guys are arguing the same point, and you're both right. As long as theres one stock piece in the exhaust left, thats what will be holding back flow, and replacing that will determine just how much creep your car is going to have.

Like I said before, some people get creep and others don't. Why that is I dont know, but that seems ot be the way it is. What I'm saying though is that it doesn't have to be the cat back thats restricted to prevent creep. It could be other restrictosn in there that would precent creep.

For example one could upgrade the CB, then the DP, and then get creep after adding the MP assuming its one of the cars that will get creep. Now if its one of the cars that doesn't get creep then you can go in any order and you still won't get creep.

Sounds like your car is one of the ones that dont' creep (as is mine, lucky for us :)). Am I making sense? I havn't slept in a day or 2 and that makes me ramble. lol

haha yeah what he said.