Made about 87hp to the wheels on a dynapak, I think my r53 throttle body may be causing it to lean out around 3000rpm then the car is dumping fuel…

I did this as a baseline before Adrian tunes the car,
current mods:
Intake with cone filter
removed center resonator from exhaust
ngk wires and plugs.
r53 throttle body
6 speed swap


all 3rd gear pulls

not sure what else would cause the dip in power….
I have tons of new/used spare parts so I may try a new coil pack, plugs, etc, may put the stock throttle body back on or my ported r50 TB….

 

I'm willing to bet the resonator delete is having an impact. As the name implies, a resonator resonates at a particular frequency (and its octaves). This is defined by the length of pipe from your exhaust valves to the resonator. When the RPMs hit a certain point the frequency of the exhaust strokes (waves of exhaust gas pressure) from the cylinders will match the resonate frequency of the exhaust pipe. When this happens you get a sharp drop in back pressure and a slight bump in torque and HP.
By removing your resonator, you have a longer length of pipe (your muffler has now become a resonator) and therefore a lower resonance. This gives you more low end torque while sacrificing mid-range torque. Exactly what your curve looks like.
BTW, the same effect happens in the intake manifold. The variable being the length of the runners between the plenum and intake valves. Many car makers have gotten clever with this and have system to effectively change the length of the runners in real time (see BMWs DISA valves as an example).

Side note, I'd also be curious to see ignition timing overlayed on the plot. If for some reason your knock sensor is generating signals the DME may be retarding the timing.
Another side note, the A/F is nearly stoiciometric up to ~3,700RPM. Re-mapping it to be richer at WOT will help with power and torque at those lower revs.

 

What you explained makes tons of sense, as the removal of the resonator also made an exhaust leak because a “quick fix “ was done so I could drive the car right away. Will be fixed next Friday at my appointment with the exhaust shop.

My only issue with the theory that lack of resonator is causing the issue related to after market exhausts. Many remove almost all back pressure and with other manufacturers and vehicles with naturally aspirated engines they still make power. But the science of the theory makes sense.

Adrian tuned the car last night but due to covid issues in our household I had to post pone the next dyno run. I put a new coil pack on the car today as well.

UPDATE:
the car was tuned by Adrian as mentioned above. It now reva up to 7500 rpm, and has launch control set to 5000rpm. Two awesome features!!!!
it starts and runs way smoother which is strange despite me not really having issues before. Maybe my old injectors were clogged.
power “feels” like it comes on quicker and smoother. The drive ability in a daily setting seems better too and smoother which is awesome, as I use this car primarily for commuting with occasional autoX. I can’t wait to practice launches and finally race again.

I’ll update as soon as I get it dynoed again, hopefully I’ll be over 100hp on this dyno lol…

 

Adriancl is great. He was able to get my cruise control working on my R50 6 speed swap. Since it is my daily driver I'm not doing anything wild to it and having CC back is great for my ankle.

 

yeah I hear that! My red car doesn’t have cruise control which is ok, but it would be nice on our 1hr ride to the beach…..

 

Finally got back to the dyno after Adrian’s tune, first pulls were disappointing. Made exact same power and the power curve was all over the place.

then I swapped the factory throttle body instead of the r53, the car immediately sounded better and the power curve was way smoother. Ended up making approximately 10whp off Adrian’s tune. Up to 97whp on this dyno




the first chart is with the r53 tb, the second chart is two of the runs done with the stock tb…

this is the first small displacement N/A car I have ever modified and dynoed so it’s very interesting to me seeing the outcome.

 

did adrian know you had a bigger tb?

 

yes he did and he suggested I remove it….

im still curious why the car is only putting down 97whp…. I’m wondering if it is just a hub dyno thing or the 6 speed swap…. Maybe even worse… the engine is tired…..

 

Isn't 97 whp about 107 bhp. That's only like 7 away from the factory specs and considering ages and possible environment factors to consider. Your torque converted to bhp is about 115-118 bhp, which again pretty much dead on factory specs (114hp).

What is the power target you were hoping for?

 

Hub dyno read lower than a dynojet

 

that would make sense

my goal was to at least break 100whp after Adrian tuned the car.

in all honesty the car drives great and I love it. I can’t wait to autocross it.

 

Most stock R50s dyno at around 100 hp to the wheels.