Power is flat after 5,000rpm or so

Sirois · Postby **Sirois** » Tue Feb 06, 2024 12:37 pm

Hi everyone,

I have an NB8B VVT.

The engine is not very rev happy, and power flattens after about 5-5.5K rpm. Revving it beyond 6,500rpm seems to just hurt acceleration.
There is also NVH from the at those rpm (more than I would think is reasonable).

I believe these have the dual length intake runners, and it almost feels like it is stuck on the low rpm runners.

Would this cause a CEL if it were an issue?
How would I check it?

The car is new to me, so I don't know if this is how these cars are, but it definitely feels like something isn't quite right.

bruce · Postby **bruce** » Tue Feb 06, 2024 12:53 pm

Dud suspension and engine? If it's new to you, why did you buy it. You should have had it checked prior to purchasing if you are unfamiliar with the cars.
Take it to a mechanic and let him have a look at your problems. It ain't gonna be fixed here on the forum.

bruce · Postby **bruce** » Tue Feb 06, 2024 1:39 pm

Sounds exactly how a stock MX5 engine would perform.

greenMachine · Postby **greenMachine** » Tue Feb 06, 2024 1:59 pm

Not sure if user is being entirely sirios ... :roll:

... siriosly trolling perhaps :lol:

.

A look at the user's posts shows lots of questions, and then the thread left hanging - like the recent suspension one.

We are happy to help posters with their issues, but there are limits. Sirios, how about post in general chat introducing yourself and your car, or a build thread for your new NB8B. The latter would a good place to ask questions about your car.

:mrgreen:

The American · Postby **The American** » Tue Feb 06, 2024 2:05 pm

A stock NB engine is not a revvy engine. It is essentially a 1.8l daily driver engine.

If it is well used, it maybe a little down on power too.

93_Clubman · Postby **93_Clubman** » Tue Feb 06, 2024 3:58 pm

Sounds like VVT might not be activating as IIRC 5500 RPM is when it should. That said, difficult to diagnose without experiencing the car.

Sirois wrote:Would this cause a CEL if it were an issue?

Don't know - try checking the ECU fault codes in the workshop manual: https://www.mellens.net/mazda/

Sirois wrote:How would I check it?

What month & year is the build & compliance plate dates? This is relevant as NB8B didn't get OBDII until 2002. If it has OBDII then get an OBDII reader. If not try this for retrieving the ECU fault codes: viewtopic.php?t=67370

Sirois · Postby **Sirois** » Tue Feb 06, 2024 4:03 pm

Thanks everyone.
And special thanks to 93_Clubman, I will follow those posts.
The car is a late 2000 build, so one of the first NB8Bs I'd imagine, without OBDII

The car was at the right price, and I just wanted something fun to drive when I felt like it.
Not being a daily driver, and having the ability to DIY a lot of mechanical stuff on cars, it fit the bill.
Also I thought if I do start liking this car a lot, I can always sell and buy a better example (an SE would be my choice).

93_Clubman · Postby **93_Clubman** » Tue Feb 06, 2024 4:07 pm

Sirois wrote:The car is a late 2000 build, so one of the first NB8Bs I'd imagine, without OBDII

Yep, IIRC Oct 2000 was the start of the ADM NB8B & yep, no OBDII, so you'll need to rig something up to read the OEM ECU, but have a look at the fault codes first as there may not be a relevant one.