SpeedracerRX7

Ok I went to the dyno with a couple of my friends on the 26th. Besides that fact that I felt completely inadequate compared to them I had a wierd problem on the dyno. I have inclueded a pic if it works of what the problem looks like. I was wondering if you experts out there think that the breakup is due to ignition, wastegate actuation, or what. It is a 15 hp breakup and I want to get the problem solved because whatever it is can't be good. I have a PFC w/commander so I can tune on it a bit but I don't even know where to start.

By the way my friends cars were a 98 Supra that put down 705 RWHP at 2.1 Bar and a 03' Cobra that we switched the pully on at the dyno and put down 385 RWHP and 440 RWHP after. There were also a ton of LS motored GM's as well as a 95 Mustang GTS that I had never seen before. Thanks for any help you can give me. I'll try to get a vid up of every run but mine because I went first and they forgot to video it.

GsrSol

I'm not familiar with reading dyno graphes but doesn't that say your a/f was 17.5?

spoolin93r1

you definately need to try to get your a/f more flat than that! it's way too jumpy. and on the big end, you're still in the 12's, but try to get it around 11:1 all the way across. as far as the weird crap happenin, i'd say the shop owners didn't have the ignition hookups right or something, because there's no way your dyno sheet could look like that and you not feel it on the street. i'm by no means a pro, but i can tell ya that

Marshall

Thats boost fluctuation! not ignition

SpeedracerRX7

Yea I know that I need to work on my air fuel a little but I am going to wait until I get my wideband put in so I can do it on the street where I get real world load. I put some fuel in on the top end and it took it down to about 11.3 at max at the top end. As far as the problem goes I know that they did have problems getting a proper signal at first because the first run only showed a max of 4k RPM. I couldn't get the lead wire on the coil so we put it on a spark plug and that made it a bit jumpy. Where is a better place to put that lead?

One other thing is that I had a slack tire on the dyno that I found just afterwards. Could that cause the problem? Thanks for the quick response.

jpandes

Damn, your buddy saw a 55 rwhp gain from just a pulley swap!

That makes me want to upgrade my pullies. From what I 've read here on the forum, FD's wont benefit much from pulley upgrades. Does someone have dyno numbers befroe and after?

Wargasm

I agree with Marshall, that looks like a boost pressure issue. Ignition related problems are usually much more jagged and don't have a nice periodic sinewave type look to them.

Did you fiddle with any of your turbo settings in the PowerFC? Probably not, but had to ask.. I'd double check that all your hoses were nice and tight with no leaks to start with.

ReDHot7

first off, i'm pretty new to the RX7/rotary scene. but, by buddy had what looks pretty close to your dyno with his 300zx. his problem was that his injectors where cutting out because they were too small for his mods. maybe this could be part of your problem..

racerfoo

my car feels exactly like its doing that....of course i havnt had it dynod, but it feels like its pulsing like that. havnt found out what it is....whats yoru boost gauge telling you?

ArchangelX

You might feel inadequate..but remember...you don't have that extra 600 to 800 lbs of extra weight to pull around.

Of course...750 is nothing to laugh at either.

SpeedracerRX7

Well I want to thank everybody for their imput. I had also thought that it could be a boost issue. I had talked to Rotorsports where I get all my work done and they could feel a little fluxuation on the top end just as the dyno breakup would indicate. He told me that It may be an issue with my wastegate duty cycle or something like that. What do you all think? If this is the problem what should I adjust and in what direction should I take it?

Just for the record my friends 03' Cobra's are supercharged and by changing the pulley I meant the supercharger pulley that took it from 8 psi up to 12 psi. Still after we put it back on we didn't dry the tires completely before he made his run (wet day) and it almost jumped off the dyno...Scary moment.

GsrSol

Yea, on the 03 Cobras you just swap on a Lightning pulley and BAM, lotsa hp!

ArchangelX

Have you seen the S/C upgrade for the 03' Cobra? Fuggin' 600hp for 3,000 buckaroos...

You might want to show your friend..pretty f'in awesome.

Domestic513

The '03 cobras come stock with a super charger, so yeah a pulley upgrade and an intake will give it a 55 WHP gain no problem. Still no match for that Supra or even the FD