tuned RX7 running low power
 

Greetings all,

I have 94 RX7 that has been tuned on 12 PSI. It currently ran 252 hp to the wheels which seems low. The turbos are 99 spec, the vehicle runs a Apex-i Boost controller and ECU and all the necessary bolt on upgrades like exhaust and intake.
The tuner is well known and has a wealth of knowledge when it comes to these vehicles, but it just seems low. The vehicle seems to drive great and the boost controller seems to show even boost on the digital read out, once you hit 4k RPM it start to take off and pulls all the way to 7k.

Any advice would be great, The car did have high intake temps and i have been told changing to a greddy v-mount and not my front mount will help gain some HP and TQ.

Again any advice would be great
Thanks
:scratch:

I'm not an expert, but I think people here could help you better if you provide a more detailed list of mods you have...

List of upgrades:

Hurley 3mm ceramic apex seals
99 spec SP twin turbos
efini Y-pipe
Racing beat down pipe and full exhaust
high flow cat
pettit racing turbo intake elbows
apex-i intake
Apex Power FC ECU
Apex Boost controller
FMIC
Koyo triple radiator

Still looking to upgrade
Greddy v-mount IC
Greddy Elbow


Thanks again all, your wisdom please
:icon_tup:

There's something major robbing power on your car. It's most likely not the tune of the computer itself, more likely something else that isn't right - a weak leading coil, old spark plugs, boost leak, restriction in the system somewhere, etc.

With those mods and boost level you should be over 300hp easy.

It could even be something dumb like a shop towel that's stuck in the intercooler - seen that one before. Or a floor mat that's keeping the gas pedal from going all the way to the floor.

Dale

Agreed.
If it were me, I'd try to better define or describe the problem.
For example, my car all of a sudden felt low on power.
From my observations, I could hear the fuel pump making some bad sounds.

Pulled the pump and saw lots of contamination in the fuel tank that was starving the pump.

Maybe you can start with the basics.
If you don't hear or see anything obvious, start with either a compression test or even easier, a boost leak test.

So the hard part is, there doesn't seem to be a problem. The vehicle starts runs and holds boost up to 7k, at 7k RPM and above it sometimes flutters the boost but once you shift it pulls and holds again.

a compression test was ran before the turbo was replaced to insure a strong motor and there was no issue with compression, and there is only about 30k miles on the Mazda factory installed motor, installed in 2012.

I just had the vehicle tuned along with the turbos replaced last week. During this we did find three vacuum leaks in the intake / throttle that were fixed with new gaskets.
the spark plugs and wires were replaced and the Pettit racing vacuum line kit along with braided turbo oil lines installed.

Again it doesn't seem to have an issue in its operation side, it just seems to be under powered. But again the tuner is well versed in the RX7 and the Apex-i ECU.

I was told that my FMIC was maxed out as far and cooling ability and because of the length/ size of the piping, I would need to change to a shorter one (greddy v-mount)
and with cooler intake temps i should see more power?

I guess I am just worried about building more into the vehicle when so many others seem to already be getting more power.

Thanks again all, let me know if you need any more info from me

A different intercooler isn't going to help. Piping length can make a difference in response, but it isn't that much.

Something fundamental is not right, again look at my post. Also you mention pulling to 7k, it should pull to 8k.

Do you have a dyno chart?

Dale

https://cimg8.ibsrv.net/gimg/www.rx7...f66900c8d2.jpg

Here is the graph I received, all of this work was done over the last 8 weeks and the cost was fairly large by the end.

I completely agree with you, that something is not right, but I don't know where to go from here and the shop is telling me there isn't anything wrong with the car itself, again the KPA reading on the Apex- I boost controller reaches 82. so almost 12psi.

Thank you for taking the time, I have checked to make sure there isn't any blocking of the gas pedal or something noticeable I can see from the top of the engine bay.

I hope the graph can give you some insight.


-
GN

Also the motor is not ported, only the apex seals are upgraded.

Compression test

What were the tuners comments ? He should have an idea what is holding back the power.

My kids are similar. I've got downpipe, high flow cat, exhaust, rewired Supra pump, and a Greddy v mount and I made 311whp at 14psi. AFRs seem a little lean (11.3-11.5 is what most go for mazda spec being 10.5). As said, could be something simple like a rag in the intercooler, old plugs, dirty fuel filter (would have to be REAL dirty), throttle improperly adjusted (too loose not allowing it to open fully).

Knock and everything else is good I imagine?

matt

Tuner told me that the intake temps were high and the IC was maxed. I would need to fix this to gain more power.

:scratch:

I will be back at the shop on Saturday, I will try to get pics of compression readings.

I agree that it seems wrong and the car doesn't feel totally happy, feels muzzled. If there is knock or anything else is not good the shop did not share that info with me nor was it in my receipt.

Assuming decent compression numbers, it's got to be a flow restriction somewhere. If it were me I would pull the mid pipe off and check to make sure that the cat substrate wasn't melted or broken. Also make sure that the air supply hose from the airbox to the rear turbo pipe is not collapsing.

If that was okay, then you might want to look into borrowing a different catback and throwing that on ... it's a real big longshot, but if there were a manufacturing defect that had the piping misaligned then that could be choking the exhaust.

I guess if it was 'tuned' it probably doesn't matter, but you didn't mention fuel mods. And wouldn't compression tend to be down with 3mm seals? Wondering if those were necessary for 12psi anyway, but that's another matter.
My first thought was a blocked cat as well.

Agreed, that high flow cat is worth swapping out, as well as pulling the elbow to ensure the TB blades open fully. Which FMIC are you running?

Also, those 99 spec twins are standard ones yes? i.e. nothing 'SP' about them?

The 99 twins are pretty damn similar to USDM twins and won't make insane power at 12 psi anyway. You're definitely down on power a decent amount though (50ish rwhp), agree with you there.

Is the TUNER the same guy that did the work? If so, seems like he should have just as much insight as anyone on the forum. And the minute he saw the graph he should've started checking stuff.

my apologies, yes the fuel system is upgraded
•Competition Fuel Rail
•Bosch 1680cc injectors x2
•Fuel Pressure Regulator
* Walbro fuel pump
all from the rx7 store

No they are the 99 spec 'SP' turbos from RX7.com
and the goal with the car was to make 300 rwhp. I am not trying to get a crazy number.
Everyone on here has seemed to say I should make that with out much issue.
I am a bit worried they are just taking me to the cleaners. :scratch:

The tuner is not the mechanic but they are the same shop. The tech who has been building the vehicle works for Intec Racing and the tuner owns the business.

the FMIC is also from the RX7 store, it is their (greddy M spec) style FMIC

So you have the second ones listed here, with slightly larger compressor wheels:

RX7.COM | 93-95 Rx7 Turbo

You're definitely down on power, but I doubt anyone is intentionally 'taking you to the cleaners.'

FDs are just pretty damn complicated cars for non-specialty tuning shops. One that's not stock and OEM will have more issues commensurate with the number of mods installed, especially those installed in a haphazard fashion.

Agreed on the cat :icon_tup:

I'm not sure where this '3mm seals make lower compression' thing started...... I think it's from ignorant (or dishonest) sellers trying to foist off their poorly built engines on an unsuspecting populace, personally.

3mm seals do have a single spring behind them, but many (like 30) years ago the FB GSL-SE (which ran these seals from the factory) made great compression, comparable to their 2mm variety cousins. There is no change in Mazda compression spec for thickness of apex seals that I'm aware of :)

Now, on an FD with 13B-REW rotors and 2mm slots that haven't been milled 100% correctly on center for the 3mm seals.....that may be one cause for the poor sealing.

P.S. also in agreement that your FMIC is just fine for two tiny turbos pushing a near-stock 12 psi boost. Anyone telling you that that's your problem..... well, I question their judgement ;)