viprez586

iTrader: (5)

Well I just got back from the dyno, with terrible numbers. (155 hp, 118tq)

Specs:

• RB Rev8 catback
• RB Revi Intake w/ cold air duct
• NGK Iridiums replaced 200 miles ago, and de-carboned
• OEM coils with 20k on them
• Mazdatrix spark plug wires
• 65*F, 47% Humidity, 856ft above sea level, 29.15in HG.
• Runs done in 5th gear
• 6spd, 65k
• DSC + Traction control off

So I'm curious how I can approach Mazda to get them to do a compression check.
I think I'll just complain about lack of power, horrible gas mileage, and it won't hot start - IF they ask me why I want a compression check done.

Unless someone wants to borrow me a compression tool for a small fee?





And I also got a very crappy video of it. Everyone at the event was scared that it revved so high, but got a lot of attention nevertheless. Meh, just weird the dyno plot is so choppy. I can't believe how pig rich the thing is too!

supergoat

Wow. Definitly go to Mazda.

I remember Darin P. using his low dyno as part of his argument for a new engine a few years back. (he got one)

viprez586

iTrader: (5)

Yeah it takes a good 8-10 seconds of cranking to hot start it. And I noticed my oil comsumption seems oddly high, but I'm going to run a test on that.

supergoat

Best of luck buddy! Let us know what happens.

alz0rz

iTrader: (41)

Even though the coils only have 20k on them I'd still point at them because that is an awful curve and I'm not talking about its magnitude. I also thought it was standard to get it a dyno done in 4th due to gearing?

viprez586

iTrader: (5)

It's standard to due 5th gear because it's direct drive aka 1:1 gear ratio.

MazdaManiac

iTrader: (3)

While that is essentially true, almost all dyno runs that have been done on the RX-8 are in 4th gear because of the incredibly long ramp time (and very high drum speed) in 5th gear.
You would be spinning the drums at 164 MPH at redline.

The effective gear ratio doesn't really matter.

viprez586

iTrader: (5)

Well, I just tried the backyard mechanic style compression test.

I took out the little schrader valve and the results were consistent on all three rotor faces for both rotors, However the front rotor pulsed to 60psi, whereas the rear rotor pulsed to 45psi max.

FRONT ROTOR:
http://www.youtube.com/watch?v=rt4OlO0Omfk

REAR ROTOR:
http://www.youtube.com/watch?v=azJWYZSnvZY

I was curious too why it was such a choppy graph, maybe they hooked up the tracer on the wrong spark plug wire?)(BTW which one should they of?) Or was it just my coils going bad.

The dyno jet can spin up to 200mph, this was a brand new AWD dyno. They said it didn't matter.

MazdaManiac

iTrader: (3)

Peace-out, motor.

Doesn't matter to the dyno, but it does matter to your results. You don't have enough torque to merit a long, drawn-out 5th-gear pull.

NgoRX8

iTrader: (1)

time for a new motor

DarkBrew

Check out my dyno chart, issues involved and the solution for my car...

Start at page 9 or 10
https://www.rx8club.com/canada-forum-35/mazdamaniac-dyno-tuning-gta-spring-summer-2010-a-195294/page9/

Don't know about your compression reading...
how does the car idle?

viprez586

iTrader: (5)

118 torque isn't enough?

Well, time to schedule an appointment at Mazda, question is which one I go to.
I know a tech at one, and got him to rebuild my trans under warranty.
So I don't want to be that guy bugging him all the time, but I planned on giving him some loot to help him out. Chances are he could push it through a little easier, plus I can show him the dyno charts and shade-tree style compression tests.

laythor

DO NOT bring a dyno chart to the dealer. That's a pretty sure fire way for them to decline a new engine. Just go in, tell them you have loss of power, hard starts, high oil consumption and leave it at that. Push for a compression test but you might have to jump through a few hoops before they do it.

viprez586

iTrader: (5)

Right, I was just going to talk to the tech I know on the side, see if he'd be cool with a doing a compression test for me, for a small fee. If he asks why I'll show him my dyno sheet(he won't care, hes got a 500hp RX-7, he knows a dyno won't hurt my car, and he told me how to get my transmission warrantied)

**EDIT**
What is normal or good for this style compression test? I looked on youtube and one guys' was pulsing to ~75psi

The car idles okay, sometimes it dips and has a shudder (like when you get cold and shiver).

My symptoms:
A couple days ago we hit 86*F and humid as hell, the car was considerably less powerful, now were back to 50-60*F.
Won't hot-start unless I let it cool off for 5-10min, or just crank for like 10-20seconds(bad i know).
Bad mpg. I get 13-15mpg no matter how I drive it. When I first got it I could get 18mpg all day without having to drive like a grandma.
My last tank I got 15.6mpg which is a very slight improvement since the new plugs. I got 172 miles for about 11 gallons.

1.3_LittersOfFurry

iTrader: (4)

You need to know the RPMs

https://www.rx8club.com/attachment.p...6&d=1266716801

viprez586

iTrader: (5)

I understand that, hence me calling it the backyard mechanic way of testing compression.

Juansito

iTrader: (5)

Yay new motor!

viprez586

iTrader: (5)

While a part of me wants it to be bad compression, another part of me doesn't.
I just would've liked to put down good numbers so I could tell this local guy to STFU.

I'm gonna talk to the tech at mazda tomorrow, see if he'll run a compression test for me under the table.
Otherwise I'm going to test the SSV for a leak, and grab a scan tool at work to log some WOT pulls and look at the MAF.

Another thing. I looked at the MAF, intake tube, and throttle body. All are clean.

shadycrew31

iTrader: (6)

If it makes you feel any better most guys with no tune get around 180 and a well maintained engine you'll see 190. If you remove the cat with a tune you can see 200.

Either way get a new engine sooner than later, if you get one now you might be able to get another one before you hit 100k.

Sidenote: why are you worried abotu having a fast car you got a street bike!

viprez586

iTrader: (5)

The bike is fun, but I like the underdog rx8. People hate on it cause its not fast enough in a straight line. I still love it...and i'lll probably fall in love all over again with a new engine.

Anyway the individual said 170rwhp was too much and I'd blow it up. Ironic.

DarkBrew

I went thru the entire troubleshooting routine... all the usual suspects.
Using the vacuum hand pump I found the ssv actuator leak but could not accept that such a small static leak could make such a difference... However, since it was all I found I replaced it... here's the result - a big jump in MAF and load numbers across the RPM range.


IMO if your engine idles well then the compression is not causing your power loss.

monchie

Add this to the lists... "The new engine club" thread.

viprez586

iTrader: (5)

I did a quick log at lunch, I hit a max of 214gm/sec in 2nd gear up to 9k, and 209gm/sec in 3rd up to ~8.3k.
I tested the SSV, holds vacuum perfect, and starts opening as I start pumping the vacuum gauge. It's fully open by 5-8inHG.

alnielsen

iTrader: (4)

I had my car on a dyno and got a 140 hp reading. Other cars, on that dyno, were reading lower than they should too.
I recently recorded a max 220 gm/s reading on my car.

It could just be that the dyno is wrong.

DarkBrew

Hmmm... I guess you can cross it off the list...
Your dyno looks so much like mine... I was hoping it was the same cause...

My dyno run was part of a group of cars, all with APs, so I had lots of comparisons.