For what reason would power would go down so significantly, with the before and after work done by the same person, and the same approach of engine safety?

Before (tuned in August):
Single turbo wastegate venting to atmosphere and straight midpipe, dyno tuning.
7psi--265rwhp
10psi--302rwhp
13psi--365rwhp

After (tuned in January, with much cooler air):
Rebuilt motor, street port, wastegate piped back into exhaust, straight resonator (about 4inches outside diameter) added to midpipe, improved stock coil connections, dyno tuning.
7psi--284rwhp
10psi--304rwhp
14psi--331rwhp

My expectation is that if I merely added a straight resonator (not an internally-multipathed muffler as some have done) and repiped the wastegate into the exhaust, with NO other changes mentioned, that I would lose some power with high boost at top end, but not 34hp while simultaneously going up in boost.

With a freshly rebuilt motor, street port, IMPROVED ignition, and cooler, denser air somewhat balancing out the exhaust modification, shouldn't I be making similar power, if not very slightly less at the same boost in a worst case scenario? Isn't going up in boost, but down drastically in rwhp, a little odd for this situation? Taking into account the wastegate piping, the low boost likely has some of that gain attributed to an improved air velocity on theand venturi effect.

I want to be sure that I'm not missing something unique to rotary street porting that I've not heard of. Does this sound like forgotten exhaust or intake ports? Or something else?

 

What is your turbo/wastegate setup? Also, exhaust size?

Also do you have any dyno charts/rpm information and a screenshot of your ignition maps before and after the retune/engine build?

 

I hate to say it.. But....... there is always the possibility that the housings are more worn out , or the seals havent gotten to max compression yet .

Normally it really makes no sense that you are making less power . unless powerband was shifted higher then you are reving it at the dyno.. after porting , My powerband shifted 400 RPM higher onto the powerband .

 

Thanks for taking a look.

I've attached the before dyno chart, but I haven't received the after yet.

I have a TD06 complete kit, and am not sure which wastegate came with it. The exhaust is a 3inch downpipe, 3inch midpipe with resonator, 3inch Racing Beat cat-back. It's hard to recall what exactly my turbo/wastegate setup are since things lasted under a month, but I'm expecting the car back this week.

Fortunately, I do have some PowerFC backups of the original maps somewhere on my old laptop, so I'll grab those and post the before and after when I make a backup of the current maps.

I was told that the seals were all showing as 8.0 on a Mazda compression checker, on a warm test--good for a rebuild, right? I understand that 3mm seals won't necessarily seal as well in the long run, however, this power change on fresh seals is perplexing. The after rwhp numbers I was given were the peak numbers for each run. I didn't think about the powerband possibly shifting, so hopefully I'll have the dyno charts soon. One housing, Im told, is brand new for the rotor which failed, and the non-failed rotor is using the same housing because, as I was told, it was found to be in good condition.

 

Here's the AFTER dyno chart. The numbers have changed, slightly, from what I was originally told.
7psi--283rwhp
10psi--307rwhp
14psi--335rwhp

 

look at those 2 charts the First one the BEFORE Chart the max power was made at 6500 , the new chart at 6300 why is that ?

it should be the opposite . did they let off the gas ?

but regardless at 6000 you are making less power then on the previous dyno .

 

One thing I do know is that rotarys don't like exhaust leaks from the block to the header. Turbulence will kill flow. Did they re-use the old exhaust manifold gaskets?

 

I have seen on the club other members lose 40hp @ wheels on the top end from routing the wastegate back into the exhaust.

Try dyno-ing the new tune and motor with open wastegate as the first set up was.

 

The wastegate is a good place to look, but could a bad tank of gas be the cause?

 

Wastegate, resonator or ignition struggling up top. Likely a restriction as you made more power on the lower two boost settings this time around.

 

Try dyno-ing the new tune and motor with open wastegate as the first set up was.

To be clear, you should re dyno tune, not just dyno again as there will be a (positive) change in the system volumetric efficiency with the wastegate open dump.

 

First thing that comes to mind. Tune, boost leaks, ignition. Look at the top of the new dyno. There's something amiss. Why does it randomly choke at 6,500 RPM when rotaries make peak power over 7,000 generally? Was the dyno calibrated properly? Were the wheels slipping? Find it and you'll find your HP but it could really be anything.

thewird

 

The new dyno seems like boost comes on later. Did the builder inspect the turbine housing on the turbo for damage?

thewird

 

Porting an engine moves the powerband to the right.

 

I would check for boost leak, exhaust leak, or ignition problem in that order.

 

Compression Check?

 

You have have some of the most knowledgeable FD owners/tuners posting respones right above your response questioning a compression check...

I would suggest following their guidance and then doing a comp test if it makes you feel better...



J.

 

I would be shocked if it had anything to do with compression. Ive seen cars that wouldnt hot start due to low compression still put up good numbers. It made more power on the lowest boost setting, its a restriction somewhere or tune/ignition issue.

 

+1. My first FD only gained 15whp at the topend from an engine rebuild when it had low compression. Low end/peak torque, boost response, and starting improved tremendously though.

I would look for a boost leak first and convert the turbo setup to atmospheric wastegate dump/retune second.

 

an interesting situation...

first off, your power distribution at each 500 rpm from 5000 to 7500 is very close meaning, to me, there was very little porting done. i worked the numbers and have an excel line graph and the two runs are close to identical as to where your power is distributed.

further, my library of 60 dyno sheets (which excludes peripheral and bridge ports) and is mainly an assortment of "streetports" is way different. less power early and more later.

so porting is not your answer.

your overall power across the curve is off 7.8% and the deficit is fairly constant aside from a blip at 6000.

there are numerous explanations.

i think plumbing the WG into the exhaust is near the top of the list. at 14 psi boost lots of flow is being diverted and it depends a bit on your manifold design etc.

it could also be the dyno, the calibrations, tire pressure, fuel, AI?.

power diff between 13 and 14 psi would be 3.6% assuming everything was really constant... which it never is.

can you post your torque curve for the runs?

hc

 

You may find this thread useful.

https://www.rx7club.com/single-turbo...power-1007928/