tphan

Again, thanks for the abundant information available on this board, couldn’t have done the install without it.

Anyway, the pipe is on, test drove the car last night, everything seem to be good. So far I don’t notice any difference in sound…but the car seem to be a bit faster.

IMO leaving the studs on simplified the installation. HKS dp was well made which also help. Using stock hardware was fine too. Use plenty of WD40, Liquid Wrench, etc…overall the whole process was smooth without any major road block.

One important tip, allow yourself plenty of time…take a walk/come back later if something stuck.

Beside Apexi intakes, downpipe, next mod is a Racing Beat dual tip cat back…from the search I think the stock ECU will be ok. Don’t have a boost gauge yet but will get one probably before the catback installation. Will the car be ok with stock ecu with those mods?

TIA

Sweet7

Get a boost gauge ASAP. Its a must whether you are bone stock or single-turbo. You'll fine fine on the stock ECU with those mods. It usually only when you are running full-exhaust(aka including midpipe) and intake that you start to see some boost spike.

DaleClark

iTrader: (55)

Might need to look into a boost controller. With a cat-back and downpipe I had spiking at transition - boost controller solved that pronto. With an intake you'll likely have more of a problem.

Glad the downpipe went on well - I've installed 2 HKS downpipes, and the fit is GREAT on those.

Dale

DaveW

Definitely get a boost gauge before you install the CB. You should be OK with the stock ECU AS LONG AS YOU KEEP THE BOOST BELOW ~10 PSI.

You may need to increase the WG pill size, or even install a boost controller (electronic or ball-spring-type manual controllers work better than needle-valve types) to keep the boost at this level.

superfastrx7

Did you get your downpipe coated or wrapped? Just wondering. I am getting and HKS pipe and thinking about just dropping it in. What's the benefit of a cat back? How much louder would it be with it? Thanks.

Glad to know the installation was pretty much straight forward.

DaveW

I got my (bought used) HKS DP Jet-Hot 2000 coated (inside & out) to insulate it and to prevent corrosion.

IIRC, a CB should be worth ~10HP. Noise level depends on the type - they vary quite a bit.

tphan

I was thinking about have it coated but back out...spent 8 bucks on a can of high heat...like Rynberg said...don't bother...it all burnt up in first 5 minutes.

There are some other good dp out there but I am very happy with the HKS.

dgeesaman

iTrader: (7)

It will be close. I suggest you put on the boost gauge and monitor the boost before/after.

You might want to drill out the boost pills a touch or go MBC like DaveW said.

Dave

live4boost

iTrader: (2)

I just installed a DP on my FD also. I already had intakes and a greddy catback. After I put the DP on my boost would spike to about 14 psi. So I had to go back to the stock catback to try to tame the boost creep. I still hit close to 14psi with the stock catback though. Ideally I would like to just port the wastegates, but I'm hoping there is an easier solution.

DaveW

Quote:
"I just installed a DP on my FD also. I already had intakes and a greddy catback. After I put the DP on my boost would spike to about 14 psi. So I had to go back to the stock catback to try to tame the boost creep. I still hit close to 14psi with the stock catback though. Ideally I would like to just port the wastegates, but I'm hoping there is an easier solution."

Porting the WG is not what you need. You need a boost controller (electronic or ball-spring MBC). With your mods, the stock WG is adequate.

RX 4 Speed

quick question for you guys... I was speaking to a tech at RX7.com. I was looking into a boost controller too. Since I have the same mods, except no intake. His comment was, if you wanted to control boost, you're better off getting a PFC or ECU upgrade, versus getting an electronic/manual boost controller. Is this true? According to him, boost controllers are good for increasing boost, not reducing boost... as in, for example, if someone is running 13 psi on stock ecu, he can't reduce to 10 psi using a mbc or ebc. I was like... I would think you could control or reduce boost to 10 psi by installing an ebc/mbc... Weird...

live4boost

iTrader: (2)

From my understanding, boost creep is caused from you outflowing your wastegate. All that a boost controller does is increase your boost by reducing the amount of airflow to the wategate, thus it venting off less boost. This is mainly speaking from an FC perspective, so is there something different with the twins?

DaveW

With your mods, the WG should be able to handle the flow. The stock system uses the boost pills balanced against duty-controlled solenoids controlled by the ECU (the stock ECU does not use the actual boost pressure to control boost, it just uses an open loop map, which is not accurate with flow mods) to regulate the pressure seen by the WG and PC actuators.

An electronic or ball/spring manual boost controller makes boost control independent of the stock ECU, and therefore, much better controlled. You can use this controller to raise, maintain stock levels, or reduce boost below stock.

I use two ball/spring MBC's, one for the PC, and one for the WG. My mods are in my signature.

Ripzta

These HKS dumpys are made for RHD FD3S. The US aftermarket 3" dumpys will actually flow better and make more HP because it doesn't have that kink for clearing the steering column on RHD. IMO US FDs will make more HP w/ stock twins.

IRPerformance

iTrader: (41)

DO NOT throw a catback on there before you address the ecu issue. Eventually you will blow up.

DaiOni

with hks dp and catback (HKS sp) I got 14.7psi (spiking, but usually 14psi peaks).

Better to be careful, than stupid/sorry.

live4boost

iTrader: (2)

Thanks for the info DaveW, that is very helpful. I have owned many FC's but this is the first FD. Do you have a diagram of your setup? Also what is the benefit of running one boost controller to the PC and one to the wastegate actuator? Are both needed, or just the wastegate actuator? I have made a pretty nice ball and spring MBC, so I will give that a try. So I'm guessing you also eliminated the pills also right?

DaveW

1. I don't have a diagram, but it's pretty simple:
a. The ball/spring MBC's go in the lines that had the pills originally.
b. The MBC inlets are fed by the two 6-mm lines coming from the turbo exit to the IC, and the controlled-pressure lines go to the PC and WG actuators.
c. The rubber tube from each actuator to its solenoid is plugged near the actuator (I used a "pill" with no hole stuffed into each rubber tube).

2. The advantage of running 2 MBC's is that you use one to control the primary boost level via the PC actuator. This, for me, eliminated any spiking and allowed me to dial in exactly what I wanted for primary boost (11 psi). The second one controls the WG (set at 10 psi).

3. The pills are no longer needed.

See this thread: https://www.rx7club.com/showthread.p...ost+controller

Retserof

iTrader: (1)

I got boost spikes with just a Pettit downpipe. The post-transition spike was big enough that in cold weather (40F) I would hit the overboost fuel cut around 5,500- 6,000 rpm during 3rd gear runs.

I replaced the wastegate actuator pill with larger and larger Holley jets until I got it under control with a .072 " jet. Then I installed a Racing Beat twin tip catback and tested the car to see if it made any difference. I think I'll be OK without further changes in the pill diameter, but I'm not real happy with the initial spike on the primary turbo, so I may try a different pill size in the other actuator line.

Get an accurate boost gauge next and take it easy until you do something to limit those spikes.