Hi Everyone, here's the low down.

Factory ECU, Yes, I know it should be replaced, just don't have a spare $10k (Edit: it's 3k, what was I thinking) for a Haltec right now, stock twins, full engine rebuild with all hoses, vaccum lines and all reliability mods. Car originally came with an after market full 2in straight through exhaust from the factory DP back.

The factory DP was replaced with an REAmameya stainless Power Expander DP (3in chamber, necking down to factory 2in pipe and flange) to help lower under hood temps. Since doing this, I've experienced boost spiking on transition to 14psi (test drives were done on a hot afternoon).

I've already decided to remove the turbos and port the wastegate, but wanted to put it out there for opinions.

If you were in this position, would you:
- Port the wastegate?
- Add a boost controller?
- Put the factory DP back on?

 

The easiest solution is a boost controller. Or just replace the wastegate actuator hose's stock pill with one that has a larger diameter opening, if it's a 1993 or 1994.

 

My experience is boost controller wont be able to eliminate boost creep from unrestricted exhaust.

I would leave the down pipe in and put in a stock or highflow cat section in and a nice catback.

You may still have some wonky transition/boost from the stock ECU then, but you can put a Hallman Pro RX MBC on the wastegate line and another on the pre-control replacing the factory solenoids and dial in a perfect boost pattern.

I had 3" downpipe, catback, larger stock mount IC and dual MBC at 10psi for years and loved it.

 

Ported wastegate, aftermarket DP, highflow cat, gutted catback, no boost controller and my boost is rock solid

Edit: The above is on a PFC. I would not recommend these bolt ons with a factory ECU. Possibly a catback such as Racing Beat. That's pretty much it, but you don't have to worry about boost either

 

Agree, hands down. Blue is right, a BC doesn’t control creep, only spike.
And just source a hi-flow cat, and one of the plethora of decent affordable stainless cat-backs that are available...and ditch the rusting nastiness you have. Both can probably be found used if you’re on a budget. It will probably sound better, fit properly, last the life of the car and should solve the creep issue without all the trouble of pulling the turbos for porting. Exhaust studs WILL break, reusing gaskets can often lead to leaks and new gaskets are really expensive.
The final plus is that you don’t need to hurry on the ECU, the stock one should do just fine as long as it’s kept at stock boost.

And I’m not a tuner or familiar with Haltech, but 10k? Wow. PFC’s are a 10th of that, have a broad knowledge base and alot of history of being just fine for a mildly modded street driven car.

 

Lots of good options here.

Look at getting a PowerFC, you don't need a full Haltech setup for what you are going for. Also +1 on getting rid of that rusty exhaust - that is some muffler shop junk. Fine for a fried up Combe (I'm trying out my Aussie slang) but not for a Japanese supercar.

If you want something short term and zero dollar, just remove the pills. You'll have less boost but you shouldn't be spiking. Or even easier, unplug the waste gate and precontrol solenoids - they bolt to the upper intake manifold.

Dale

 

Full exhaust with the stock ecu is asking to blow up. A boost controller or ecu will do nothing to keep boost in check if the wastegate cannot handle the flow. The easiest thing to do is to install a restrictor plate in the exhaust. You should still at the least get a power fc and a solid tune to be safe with those mods. https://jp3motorsports.com/products/...strictor-plate

 

OP what kind of intake do you have? stock airbox is a simple solution.

 

His air box wouldn’t have anything to do with his creep issue...that comes from the exhaust side having too little back pressure. Spike is from the intake side.

 

maybe get one of these??

https://jp3motorsports.com/products/...strictor-plate

 

it's tough to understand fully what's going on without datalogs, which are not normally possible with the stock ECU. it may have multiple things going on.

OP is your stock downpipe similar to USA style with a pre-cat or is it JDM style, no precat? You are in Australia so I'm not sure which it would be.

 

Thanks Everyone for the replies!

What was I thinking!?! 10k for the Haltec was pretty pessimistic. The Elite 2500 with conversion harness is 3k... (Still a little out of budget right now)

I'm more comfortable with the Haltec Elite than other ECUs, and I know the Apexi is very tried and true for our cars, but there's better local support with the Haltec here. (I also installed an android head unit as an upgrade, but also in preparation for one so I can use it for minor on the fly tuning).

I want to keep with as close to factory boost as possible (10psi), not out there chasing 500hp. I like the twins as they are, with the mods done so far, I'm really enjoying the quick response, but not at the risk of detonation.

I've still got the factory DP, it has the Pre-cat chamber. The reason for the creep is because of opening the exhaust flow further with the new DP and already having a straight through system. DP was the only change on the exhaust side.

The rest of the exhaust looks worse in the photo than it really is, It's black steel pipe that wasn't painted, so it will last, but looks bad due to years of surface rust. Unfortunately inherited when I bought the car.

Off topic: Any suggestions for a nicer DP back kit? (Invidia, Tanabe, RB, HKS?) It is a little loud and has a lot of bass to the exhaust note. I'd like it a little quieter, remove the smell (only started since factory DP removed) and drone, but I do like the bassy "Thrump" it does instead of the "brap" when it's up to temp at idle.


Oh, I almost forgot for arghx, intake side (can be seen in the video):
- Factory air box
- High flowed Y Pipe (Core exchange at Pettit)
- Air pump delete (because of the high flowed Y Pipe)
- Blitz SMIC
- Factory pipes and replaced silicone with T-bolt clamps

 

The factory downpipe with cat in it is a liability- those close coupled cats ge too hot on the rotary and crack and clog up the exhaust.

Better to use the downpipe you have and a highflow cat or stock cat on the main cat position.

A big oval muffler will provide the exhaust note with the moat bass and least high frequency brappyness.

I recommend Tanabe medallion catback.

 

I recommend a high flow cat with the air pump functional to keep the smell down. My car smelled no worse than stock with the RX7store / Bonez cat and emissions intact. Once I pulled the air pump and ACV things got stinky.

I know some people have had good results getting rid of the smell with different main cats and no air pump.

If you decide to try PFC there is an amazing program for it now called FC Tweak that has autotune and many other great features. You can get a PFC and Tweak software for 1/3-1/2 the cost of your option.

 

The bonez cat with the air pump hooked up is good to go. No smell, no boost creep.

I don't think the downpipe is the problem here, its definitely the open exhaust. OPs downpipe doesn't look that different from the HKS I use, and with the highflow cat I have not had any boost creep issues. I also have the RB catback.

 

Bonez cat, RB dual.... PFC with FC Tweak.... all the support you need. RX7.com (Ari) and Xavier for FC Tweak.

 

Thanks everyone for the feedback, unfortunately at this stage due to having the Y Pipe hi-flowed I can't put the Air Pump back on as there isn't space for it.

I have already pulled the turbos, ported the wastegate and put it all back on, but have now decided to replace the exhaust as well.

As recommended, I'm looking to go with
- Bonez 3" Cat Midpipe from RX7.com
- Tanabe Medallion Cat Back

Just wanted to confirm if the flanges are stock sizes and if anyone is currently running this setup happens to have a video so I can hear the exhaust note?

 

Yep that setup will all bolt together.

For the high flow cat if you are in Australia I'd look for options that are in your neck of the woods to save on shipping. The Bonez cat is nice but it isn't anything super special.

The Tanabe is a nice, mild sounding exhaust. You will be happy with that.

Dale

 

Cheers Dale, greatly appreciated! 🍻

I'll take some video on the exhaust before and after.

Looking to pull the trigger on the Haltech Elite 2000 with stock ECU harness conversion shortly as well. Going to be a fun summer down under this year 😄👍

 

Well, I was informed today by Andy's Auto that the Tanabe Medalion Tourning is no longer available, but they asked if I was interested in substituting my order for the Revel Medalion Touring-S

They were nice enough to send pictures and links, I was very happy when I heard it in the video. Turns out it's the deep tone I wanted to keep, just quieter! Super happy!

Here's the videos for comparison
Tanabe Medalion

Revel Medalion

 

so.... you still planning to do this on stock ECU? If you do, do yourself a favor and keep the stock airbox and filter to keep the boost down.

 

I'll be keeping the stock air box, and it's still currently the stock ECU until the Haltech Elite 2000 arrives. I can confirm that since porting the wastegate the spike / creep has smoothed out and is now only boosting to 11psi instead of the 14psi I witnessed when transitioning.

I haven't leaned on the engine too hard since it doesn't have much run time after I rebuilt it, plenty of time at idle at the moment, maybe 1 mile (1.2km) of driving time while shaking it down (Leak checks and suspension tuning).

I'm hoping for a response from RX7.com soon on the Bonez Cat order to be able to replace the whole exhaust system.

 

Not sure if you're aware, in the news the other day, lots of stuff ex-USA, is being returned to sender and the only option was courier.....I wouldn't like to be paying for an exhaust system flight at present!

The thing in the exhaust, looks suspiciously like a resonator rather than a cat. As a temporary measure if that's the case, I'd probably look at getting another one welded in to assist with boost control. Not sure where you are, but Walkers sold me one donkey's years ago and any decent exhaust shop shouldn't have issues. Could even try James to see if he has anything shiny https://www.facebook.com/FDRX7Parts

To repeat the others, playing with fire with the stock ecu

 

Cheers Billyboy, I've been keeping a keen eye on the shipping at the moment and found the biggest hold up is if it's coming in via Melbourne (Turns into a 5 day wait when it lands) but all my recent purchases have come through within 2 weeks.

On my current straight pipe, yes, it's a "Hotdog". It's as it was when I bought the car, except I've removed the factory pre-cat for a down pipe, which was the initial cause of the creep.

I've already had the Turbos back off and ported the wastegate which has helped, but putting a midpipe cat and the cat-back should be better insurance and make the car more liveable as it sounds like a Harley right now.

Once that's all out the way, Haltech and tune 👍

 

This evening marked a bit of a maiden voyage. Just a 10km drive to put fuel in and back home again.

Under idle and low load, there was vaccum (around -0.6 PSI) and running out to 6k rpm saw 0 PSI in 1st gear.

2nd Gear pull saw 12 PSI - 10 PSI - 12 PSI, transition was very smooth, secondary was pulling hard!

Both pulls were done at around 3/4 throttle to keep an eye on boost levels, AFR and was done on the stock 8-bit ECU (which is being replaced, along with a cat midpipe and cat back system in the next few weeks)

So, to answer the original question, Porting the wastegate is a better option over putting the stock pre-cat system back on.

I'm fairly confident that putting a more sensible exhaust system on will be better insurance on top of this rather than adding a restrictor plate in the exhaust.

And, most importantly as echoed by the awesome members here...

Don't play with fire, install an after market ECU and get it tuned!