386 RWHP @ 13PSI, Turbo-NA w/GT4088R, Aux Bridge, etc.
 

This is basically a copy and paste from my buildup thread with the addition of the dyno sheet.

On Monday I booked some time at Chandler Techologies to run the car on their Dynocom dyno. I was initially worried that the day was not going to go so well as my passenger side front caliper stuck on the way there (what the hell? Seriously....) but then again, you don't need front brakes to dyno a car!

After the car was strapped in, the baseline run made 320 RWHP at 13 PSI. Much more then was expected (I guessed it would make 266, others guessed 275) keeping in mind that the current "tune" in boost just meant that the A/F ratios were barely registering on the gauge at something other then 10:1 flat.

With each successive run we pulled a bit of fuel and gained between 10 and 20 HP every time. After approximately 6-8 runs (I lost count) the final number was 387 RWHP, 279 FT-LBS @ 13 PSI. A conservative estimate puts that right around 420 HP at the flywheel. Not half bad for an hour on the dyno on low boost. A/F ratios are in the mid 12s until about 5 PSI, falling to the mid 11s to 10 PSI, then low 11s to 13 PSI. Timing is still VERY conservative at 10 degrees. I could put a few degrees of timing into it right now and pick up a few more HP but I'd rather wait and borrow an EGT gauge (or buy a cheap one) before I start bumping timing too much.

The video from the last few runs is available to download in two formats. The first is a high quality Windows Media file and is about 15 MB in size. You can really see and hear things the way it took place (the whine from the turbo is unbelievable). You'll probably want to "Right Click, Save As" to download it instead of opening it directly in your media player. The 2nd link is the same video on YouTube but the quality is not that great (especially the audio).

Project Tina First Dyno Runs (WMV High Quality)

Project Tina First Dyno Runs On YouTube

The next step is to install a boost controller and crank that turbo up to 17 PSI where it belongs. I fully expect 500 HP to the wheels once I get into real boost...

If you look at the dyno sheet, the torque curve is very intersting. Quite flat once the turbo has reached full boost. My only annoyance is that the wastegate seems to be stating to open around 8 PSI which is introducing some lag. This will be fixed with a boost controller.

Your car sounds so sweet!! Nice Job!!!!

Wow, really impressive. The long, detailed build has finally paid you back in excellent power... You deserve it. :)

Cool vid. I know you're planning on uping the boost, but even now, what are your driving impressions? Are you glad you went big turbo? Just curious. :D

that is insane. I'm sure you've been asked, but how much boost do you plan to run after it's tuned. I'm assuming you'll tune w/ pump gas? I can't imagine how much c16 must cost up there.

Impressions of the car...well, it's terrifying. :) Because I'm still using an open diff (the stock diff that came with the car) there is a lot of drama at anything more then 50% throttle. Tires squealing, smoke, rear end stepping out, etc. But once the car gets traction it pulls like there's not tomorrow. Forget trying to look at the tach during 1st and 2nd gear. By the time you've kept the car straight and have some time to look down at the tach you're already at 8K. Generally the 1st and 2nd gears need to be driven using the overrev buzzer.

There is some lag in this setup, but mainly that seems to be a wastegate issue. It is opening up quite early (as expected...a 13 PSI spring isn't an on/off switch that goes from full close to full open at 13 PSI). A boost controller and lower pressure spring will clear that.

I need a LSD of some kind. There are several options for the NA diff.

Drivability is really issue free. There's a few times in traffic where I can catch the idle while letting out the clutch so the car will "pig root" a little, but aside from that it starts and drives as if it was stock.

I'm happy with 13 PSI right now and there's not much point in increasing it until I can fix the diff. But I plan to run around 17-18 PSI for around 500 RWHP. With conservative timing I don't expect any problems with pump gas.

Running anything but pump gas it simply not an option since this car is a driver. I take it to work, haul stuff in it, etc.

He says right in the inital post he is going for 17psi....

BTW very nice work....

Are you planning to stay with the 7" rear diff?

It will be interesting to see how that holds up if you are. I would imangine you have already answered this question in some detail somewhere else.....(probabl more than once)...

One more question, does that specific Dyno have the ability to sense clutch slip? (reads spark plug wire for engine RPM like a timing light does)

I would worry about that, if you are running an NA transmission especially.

Even if the clutch will hold to break the tires loose in the first 3 gears on the street a Dyno can make it slip pretty easily.

makes no sense to decrease the spring if your going to increase boost
a electric boost controller has a gain feature use that to adjust response

On the good ones the setting is called "Gate Pressure Point"

You can actually set at what boost you want the wastegate to start opening...

But, if not careful you can program in your own little low RPM boost spike... ;)

I want to also have a "very" low boost setting for use in the rain or when traction could be an issue. Hence the lower PSI spring.

In reply to your earlier post, I'm not too worried about the differential right now as far as strength goes. The NA diffs have been shown to take a lot of abuse from things like V8 conversions and they rarely seem to break. The TII unit is of course stronger but I'm fairly against having any TII parts on this car. If I have diff issues, I'll rebuild it with an aftermarket center section and have the gears treated appropriately.

I have not seen any indications of clutch slippage either on the dyno or on the street. The copper 6 puck seems to be holding up just fine.

As for the NA transmission, I'm not worried really. It's already been abused a lot this year and seems to be as happy as ever.

I figure if it's not slipping in 5th gear under full boost, it's not going to slip on the dyno in 3rd either. :)

The difference of course is they strap the car down and sometimes unrealistically load the car to ensure a safe tune under all conditions. So they can load the car up even more than it would be with two people under full boost in 5th gear in a head wind. This is where my tuner sees cars clutches slip a lot. It is nearly impossible to percieve this especially with good clutches. There is no indication in the drivers seat that it is happening but good dynos have the capability to detect it by monitoring RPM signal. Less experienced tuners end up actually miss tuning engines this way.

They say it happens with those silly guys that turbo thier hondas and still have these dinky little clutches. Even with a "good" clutch and no slip on the street it can happen on the dyno. But it can also happen inperceptibly on the street too...

:lol:

I don't know what to tell you. :) Having the clutch slip is one of most minor concerns that I have regarding this car. The fabricated copper 6 puck (sprung of course) that is used in this car is something that has been used in a lot of RX-7s (and some nasty Supras) locally and it seems to hold up quite well. Could it be slipping? Maybe. Is it noticeable at all? Nope. :) The tach vs. speedometer on the dyno was completely linear so if it did slip, it wasn't much....

Why this concern about the clutch?

I think they were a little wussy on the dyno brake, to be honest. Next time I'll have to make sure to get them to really load the car because there was a noticeable lag in boost.

I'm not sure what that means. Are you saying I'm wrong? Or right? Because there are a lot of 11 second cars running the NA diff...

congrats Aaron keep on proving em wrong!!!! :icon_tup: NA turbo power!!!

the N/A units that do NOT break are the open diff units, because they can let one wheel spin and release the torque that would rip an LSD apart (stub shafts FTL).
you really need a TII clutchpack all freshly rebuilt in there if you plan on doing any hard launches.

good luck on the project man it sounds like an animal! WOOOHOOO!
rock on!
more pics!
:)

I think you will probably find out quickly enough, and it was just a thought for discussion. I was not predicting anytihng. I would guess a good clutch setup even in the N/A transmission is going to hold quite a bit of power.....

ive been told that the higher compression N/A rotors dont mesh good with high psi and that if you plan on going above 8ish psi you really risk alot of knocking, is this true? thanx.

Wow, that's very impressive...great work!

That makes sense, and is kind of where I'm at right now. First one wheel lets go, then they both do. :) Makes for some fun driving, but slow E/Ts in the 1/4. I'm quite against having TII parts on this car so what I will likely end up with is an aftermarket center section and then a set of shafts made by the local driveline company.

More pics?! There's already more then 500 out there! :)

The transmission seems to he holding up like a champ. No noise or slop has developed and obviously it's not failed catastrophically. When I start getting more rear traction there may be some issues but then again, I've never broken an NA transmission due to power (only due to wear and lack of oil).

Not true. Like anything else, if it is tuned poorly, there will be problems.

nice job. sprung 6 puck FTW!

Nice torque curve

I'm curious as to why you didn't dyno it from idle... just to see how it reacts from going to full vacuum to full boost.

Showing the torque curve from 3K and up just seems like cheating.

is it true!>?!>?
what do you think his car is :shocking:

No reason really...The first bunch of dyno runs were started about 2.5K, but the last set were done from 3K upwards.

I don't know if I've ever dyno'd a rotary from idle. :)

Ive never seen any engine done from idle. They are always brought up to 3rd gear and then floored from about 2-2.5k.

So no TII parts huh. ;) Well, you're brave, ill give you that. Sounds like a big ford 9" is in your future...... ;)

don't be too stubborn. A $100 used T2 rear will be a hell of alot smarter than custom halfshafts and some Kaaz LSD stuffed into the N/A rear. I know your a smart guy, just loose the N/A idea thats burned into your head and go the cheap effective route.

It's not like you are gonna be in the Guiness Book of World Records for the fastest all N/A turbo Rx-7

I wouldn't trust an NA diff behind any serious amount of power. If you are cleanly breaking the tires loss it may last for awhile, but if you get any sort of traction or wheelhop, its likely going to eat away quickly. The only NA diffs that I have seen lasting on V8 swaps are with an automatic transmissions with relatively low power, and even then their days are numbered.

Any NA (and quite a few TIIs) that I have seen take "alot of abuse from a v8 swap" has ended up in pieces. Suit yourself if you want to try it.

:suspect:

^^ you know you want to admidt it makes more sense, but I guess Pride isnt Free

I believe Aaron's after the fact that so many people are against it.

Would a TII diff work and be stronger? Obviously, the guy's not handicapped. But can an N/A rear end take some SERIOUS power and stand up to an awful lot of abuse? He's proving that right now. All the people who tell the newbies around here "don't bother leaving your N/A rear in the car after the TII swap since it won't hold the power" are eating their words while Aaron burns around twon with 400bhp blazing through his N/A diff. Will a TII diff take more? Sure. But this is holding up quite well. And even a TII diff has its limits. Locals are busting axle cups on hard launches with slicks at Aaron's power level. So why bother going that route since it'll break anyways? (same mentality as the N/A rear to begin with....you see?)

The car is a turbo'd N/A I don't know what's so hard to understand :)

its all in how you drive the car. things break when you race. If you launch with a n/a rear and slicks something will break. Why would you race a 400hp car without slicks???

Lots of reasons. :) I ran 18" rims with 255 tires when I raced my 400hp TII. Hooked nicely actually....

back on topic...............---->

If I wanted a TII, I would have bought a TII or done the TII swap. It would have been a bit easier then what I've done so far. :)

I considered using the TII diff, but why? Most of them are high mileage, and getting to the point where they are just plain worn out (as are many of the TII transmissions as well...) anyway. If I'm going to have a diff rebuilt, why would I not just stick with the NA diff and fill it with superior aftermarket parts? Philosophically it's far more in line with with I've been doing with the car so far and it's going to be far better then a TII unit. Besides, at more then 400 HP the TII parts start to get a bit delicate as well...So the choice boils down to starting with an NA diff and having it rebuilt with new stuff, or starting with a TII diff and having it rebuilt with new stuff. No advantage either way except the fact that the NA unit is a direct bolt in. Then if the half-shafts break, I just have new direct replacements fabbed up and I'm good to go...

I've been putting big power in front of NA drivetrains for the past 7 years and have not had a single failure. :)

zbrown is launching his GT42 powered REW car on the anti-lag using an NA rear end and slicks. :D

Partly. I like to mess with people. To this day I still get at least one PM per day that says I can't turbocharge the NA. Could have fooled me... :)

Hell, when the car was NA I was doing 8K clutch dumps on slicks at the track. I broke my "unbreakable" driveshaft twice. :D

Bingo. Either way I need to fill a diff with aftermarket parts so there's no point in starting with the TII pumpkin over the NA unit.

If they hate this, they are going to despise me for my brake setup... And transmission selection when the NA unit finally dies... :D

The TII diff has a larger, and stronger 8" ring gear. The LSD unit used in the S4 TII is also nearly indestructible, they are commonly used as an upgrade for FD's torsen unit, and I have never seen or heard of one breaking, possibly because other things will break much sooner than the LSD unit can reach its limit. They can also be rebuilt if you are want to make sure its fresh and grabs hard.

Do what you want, I'm not trying to argue with you, just saying, I wouldn't want an NA diff in my car, in fact, the TII diff is on it way out as soon as I get some custom axles for my new rear made up, although, I have other reasons, besides strength to go with a different rear end.

Since you mentioned V8 swaps, it may not be a bad idea to take a few pages out of their book, a pinion snubber and/or a diff anchoring bracket will go a long way to help from tearing the front mount off the subframe. The stub shafts and ring gear will then be the most likely things to break. Stub shafts are fairly random, but you'll likely take a few teeth out of the ring gear before it comes completely apart, so just listen for it howling.

Then you know no people who run real power :lol: I've personally watched 3 S4 TII diff's give up the ghost at Toronto Motorsports park. One of them in a pretty spectacular manor @ half track.....and I'm not there very regularly either.

Read above statement :) And if you don't believe me, come up to the track and ask the prep team who had to scour the around for 20 minutes picking up/sweeping chunks of ring gear :rofl:

Damnm, that much power in a turboed n/a. I went the opposite way with a tii drivetrain and n/a rotors. So far its doing awesome at 19 psi on pump gas (93 though). But yours looks hella good doing it.

Reread my post...the LSD units are generally the strongest part of the diff, the ring gear is certainly not. I've seen the diff housing crack in half, and tons of broken ring gears, I've still yet to see a broken S4 TII LSD unit...not saying it hasn't happened, just saying they are damn tough from what I've seen.

plz post when your stock differential mount rips in half

Nearly, yes. But I've see a few pop. Generally the case cracks at the pinion and then all sorts of destruction happens. Or the half-shaft flange shears off...

The whole concept of the car is turbo-NA, so if I am going to swap a diff it's going to be with something totally custom and not based on TII parts.

Yep, that's next on the list. Next spring I'm going to drop the subframe and with with urethane bushings all around, with the pinion snubber.

Posts like this remind me of 7 years ago when people would say "plz post when your engine blows up". :D

I'm not saying the NA diff won't blow up, but at 500 RWHP the TII diff will too.

Keep up the good work Aaron, I love to see the progress. What a beast that car has become.

Good work!

That of course depends on the application, we run turbo diffs at 500 HP with zero problems on road courses. Drag Launches CAN certainly be quite a bit harder on drive train parts. But, for those who dont drag thier cars regularly the TII and FD units are VERY stout. Certainly nobody can argue they ARE NOT stronger than the NA FC and FB units...

I think the weaker link in both turbo and non turbo cars is the transmission. Again the turbo unit is more stout but even 300 RWHP can grenade one......seen it multiple times.

very nice!

is this on 9.4 or 9.7 rotors?

next time can you have them turn off the shading and the curve smoothing?

That's sort of the point...Depends on what you are doing with the car. I fully expect to break either diff when launching the car on the anti-lag with a set of slicks. :) But during lapping days (if I ever manage to actually get out there...) I won't be worried in the least....

[QUOTE=patman;7318317]very nice!
is this on 9.4 or 9.7 rotors?
[quote]

9.4:1

Sure, but next time will likely be next year, so I don't know if I'll remember. :)

wow aaron very impressive im happy to see what youve accomplished if you dont mind me askin what are your et's at the 1/4?

Very nice run's, really decent power.


That's a bad-ss FC :icon_tup:

nice results.

When I was making around that power level I was starting to have traction problems in 3rd, with an LSD...

If you plan on hitting up st. thomas this year and want to borrow my slicks just let me know, I see 11's in your future :)

Why are HP and TQ crossing each other at 6k? HP is based on TQ and they always cross each other at 5,252. Something is up with how the dyno is setup...

HP=TQ * rpm/5,252.

:Wconfused