MikeC

I've just had my fd converted over to non-sequential and am *very* dissappointed with the result. As it's a daily driver I spend most times in the below 4k rev range and it has practically no boost there. Once it comes on boost it is quite good but you've got to rev the crap out of it to get it there. Will a smaller single turbo give me plenty of low end, I'm not after v8 torque just a little more than standard or even the same as standard and with more top end power. Basically, I want more power without sacrificing bottom end. Any suggestions?

Thanks

1QWIK7

iTrader: (33)

as a fellow non sequentialer (lol), i know how you feel but my job and my usual runs are really close to each other and i live in a city so revving the crap out of it are not what comes into my mind when i drive. i like to take it easy when i drive on the street. when i need the power, which is usually on the freeway/highway, that power gets there when i get into the boost range.

what i would suggest is go back to sequential for now, but i heard the quick spooling singles are the t04r? correct me if im wrong..

MrRx

iTrader: (1)

Most single Turbo's dont start making power untill after 4k....Ball berring ones tend to spool faster..

b0b

many people are running singles and are making power in the mid 3k range...

how much power do you need just driving around town? you wont get much faster than 50-60mph will you?

ptrhahn

iTrader: (9)

Go back to sequential. You can still make great power that way.

BoOsTin FD

I agree, go back to sequential if you want to have power below 4k. Running sequential system is better then any single if you are not looking for huge HP numbers. That's just my opinion.

Amel

MikeC

I will almost never go over 70mph. That's why I want it to be more torquey. The stock turbos come onto good strong boost from 2 to 2.5k. The problem I had was the boost dropped to zero suddenly at 4.5k. The shop told me they could fix it by going to non-sequential and it would start to boost at 2.5k but that's just plain not true at all. I don't have a gauge but I'd be suprised if it had any reasonable boost before 4k. 99% of the time I will be driving below 4.5 k so 99% of the time I've got a car that has the power of a carolla.

Trexthe3rd

Small BB single will give you boost around 3200 rpm. But unless you are prepared to dish out the money for the single conversion, go back to sequential and fix the transition problem.

Sidestick

iTrader: (1)

Your original problem was just a simple case of one of the vacuum hoses coming loose in the rat's nest. I don't remember specifically which hose it is now, but it would have been readily apparent had you unbolted the little black plastic vacuum tank in front of the upper intake manifold to expose the front part of the rat's nest.

I, BTW have been single turbo for a while now. I make full boost (15psi) at 3.5k rpm.

I'd say go back sequential & take your car to a shop that's REALLY familiar with FDs.

sicminded

how about upgraded twins and back to sequential (99 spec turbos?). i'm guessing they are the same little lag as the stockers and able to run more boost/power efficiently.

chris

RX7 RAGE

iTrader: (22)

Are you running a straight thru exhaust with your non seq setup?

MikeC

Unfortunately the original problem wasn't easy to fix. I took it to a dyno tuner that was meant to be the expert on FDs and he couldn't solve it and actually gave up doing FDs after he did mine. I took it to the best rotary mazda dealer in town (who did the work on the 2 rx7s that mazda were racing in australia) and they couldn't solve it. They guys who did my engine rebuild did a great job on the rebuild but they couldn't solve it either. I'd do it myself but I just don't have time.

MikeC

I'm using a new downpipe and catback replacement but that's another thing I was really dissapointed in. It vibrates the entire car and makes it feel like a cheap shitbox. I'm really starting to respect what mazda did with the car originally, it was very smooth, quite, torquey and reasonably powerful.

RX7 RAGE

iTrader: (22)

hmm...running a straight thru exhaust ie dp, mp and catback makes a big difference in spooling..i'll let you know how mine spools up when I install my non seq turbos as I have no cats at all.

rynberg

Hard to believe you can't find a GOOD FD mechanic "down under"....

You want torque back, you need to fix your sequential system. It sounds like you'll have to troubleshoot it yourself. It sounds like your charge relief valve is not closing and is venting your boost back into the intake box.

http://www.autosportracetech.com/RX-...leshooting.htm

Good luck.

BTW, installing a downpipe and cat-back should NOT have the effects you described. They are installed improperly and are touching the car's body at some point.

MikeC

The guys I'm taking it to are very well regarded with rotaries but maybe not so good with the stock FD. They are more into the full racing cars.

Does anyone know if it is possible to fit a single turbo and have the same or more torque across the entire rev range?

SleepR1

LOL. This is the best rotary shop in Australia? What a copout. Not only did they not fix it, but they lied about how you're still going to get boost @ 2000-2500 rpm with nonsequential??!!

For more low-end torque. Switch back to sequential, and for God's sake get a boost gauge!

I'm with rynberg. Diagnose the sequential system yourself.

Your secondary is not coming online. It could be a simple as a bad vacuum chamber check valve.

See if your second turbo comes online by creating a vacuum with the engine. Accelerate past 5500 rpm. If the 2nd turbo doesn't come on, get out of the gas to create a vacuum (20 inches Hg), by allowing the engine revs to drop back down a bit. Then get back on the gas. If your second turbo comes on, then you have a vacuum leak somewhere. Vacuum leaks are usually associated with the vacuum chamber or the vacuum chamber checkvalve.

BUT, the second turbo problems could also be due to a bad charge relief valve, bad air bypass valve (commonly known as blow-off valve), bad charge control actuator, bad turbo control solenoid, or bad turbo control actuator. These parts usually don't fail, but these are other causes for 2nd turbo problems.

It's probably a simple matter of a vacuum hose, or vacuum chamber full of oil (sometimes this happens).

Diagnosis is a long process, but well worth it, if you can fix what the best rotary shop in Australia could NOT!

ptrhahn

iTrader: (9)

I've come to the conclusion that if you're going to keep the sequential twin-turbo system, sooner or later you will need to start learning how it works, and how to fix it. I held out as long as i could trying to get shops to diagnose everything, and at some point its actuallty easier to just take a stab at it. The Auto-tech site above is a big help. If an artist like me can figure it out, you can too.

dubulup

a small single has an ENTIRELY different air flow (than NS twins)...so yes you will make power before 4k.

Flybye

Any shop that says they can't fix the sequential system are basically TOO lazy or TOO stupid to diagnose it....

I've had 3 sequential problems.
1) Cheap silicone hose kinked
2) Same cheap silicone ripped (Replaced it with good thick silicone and been great for 5+ years)
3) Vacuum chamber nipple cracked off. (That's that stupid chamber behind the power steering pump)

And I fixed them myself. Sure it was a bitch to find them, but I still did it

I'd take it to another shop if I were you. I know 2 people that went non-seq and hated it. One of them just stepped up to a small single, the other went back to sequential.

Flybye

It's actually not that hard to figure out. The pain in the *** about it is actually diagnosing each hose, solenoid, actuator, one-way valves, and pressure/vacuum tanks.

What makes it even funner is an old hose could have a rip in it. The hose may look PERFECTLY fine and connected, but under pressure, that rip would slowly open causing a problem with the sequential system.

Another common mistake people make are testing the solenoids. Hooking up the solenoids to power and hearing them click is not enough. You actually have to connect them to a pressure/vacuum pump and test them. The electric solenoid inside may still be fully functional, but the diaphram that tells the air when it can or can not go through may be leaking. That happened to a guys solenoid I tested once. He was having a headache with his system, he told me he checked EVERYTHING and couldn't figure it out. I asked him if he pressure tested anything and he told me no. The first thing I tested was the wastegate solenoid, and sure enough, when the solenoid was supposed to be closed, it was leaking air.

HEns

hmmmm, ive never driven or felt a 7 running non sequential twins, but here are some turbo charging ideas that ive experienced. (mind you these were not fd's but other 13b rotors.)

ok, a garret gt30 will give you awesome response, a nice powerband and can produce some nice power depending on how much you are looking for.

up from that a gt35/40 produces full boost by around 3500 rpm and is capable of pulling very respectable numbers.

all that said, if you really want a lot of torque, look no further then going 20b (jks.) :P

SPOautos

non sequential will suck if you dont have a open exhaust and intake. You need to ditch that cat if you want it to spoolup better...course your not going to get full boost at 2500 non seq no matter what, you might start to see some boost there but it wont get full boost till prob close to 3500 or so. Non sequential is better from 3500-5000 and sequestial is better form 2500-3500. What you gain from 3500-5000 is WAY more than what you loose from 2500-3500 so personally I feel liike non seq is worth it.

You just need to get a mp, good boost controller to keep it at 10psi, then get them to get your exhaust off the body do ditch the noise, and start learning to use those higher rpms....they are much more fun anyway.

STEPHEN