Bambam7

Just looking for ways to reduce turbo lag... I've got tons!!
It's very bad... say I'm at 5,000 rpms and I punch it, it's good second before it's spooled up to 8 psi, if not a little bit more.
On a hard, racing 1-2 shift, it barely squeals the tires because I let off the throttle to shift, then it pulls a second later. It's really bad.
I've got a FMIC, which is two stock cores. I'm using 2" piping.
I've ditched the twin scroll, and ported the passageways a *little* bit. They aren't equal sized at all.
My ported engine has had the exhaust sleeves removed, (dumb shop) so I'd like to put those back in to increase velocity.
I'm going to be using a manual boost controller too....
Anything else I can do besides putting in the sleeves??
IC piping is very short and direct.. can't get any better.

importboi22

how many miles on the turbo? even with my S5 motor with low compression would build 9psi before 4k rpms.... and wouldnt loose any boost between shifts... i would check shaft play and see if it spins freely

Six Rotors

iTrader: (17)

Well I have this Lysholm Compressor sitting on my garage floor!Did you get the caliper piston?

scathcart

There is a type of coating said to help reduce lag quite a bit when done to the exhaust side (can't remember, it also decreases spool-up time.) You can also wrap your downpipe and your hot-side, and, obviously, get a more efficient IC core and piping set-up.

dr0x

Do you mean ceramic coating? Or that manifold tape stuff (believe that has ceramic in it also)?

Anyways... sounds like something is wrong if it takes you till 6k to build 8psi. My car on a blown motor was doing it before 4500rpm.

scathcart

Ceramic coating yes, but a specific brand of it.

You can use tape for a lot cheaper, but it makes rust form a lot faster.

I think you guys are getting lag and response confused.

dr0x

Yeah I guess I did.

jreynish

iTrader: (2)

BamBam7 exactly how are the stock Top Mounts welded together? in series or in parralell if it is in series how much or the entanks are left? because if there is a big gap between the two that owuld explain alot of it!

dr0x

I would think if the cores were welded too closely together and the passages in the intercooler werent perfectly matched, that might cause a problem too?

Evil Aviator

1) The entire purpose of the twin scroll is to reduce lag. You removed it, so you can kiss your turbo response goodbye.
2) One of the only good things about the stock TMIC is that it is excellent for response due to its short plumbing and small volume. You removed this, too. It's almost like you went through the whole book on how to ruin your response, lol. This is what happens when you do all the drag race mods to your car and then try to road race. BTW, I hope you have those two cores in parallel rather than series.
3) Squealing your tires will slow your race times.

White_FC

However, your turbo should not take anywhere near a second to build upto it's boost level if you nail it at 5Krpm. It should be damm near instant! Especially on a S5 hi comp. motor. I'd be guessing it's got something to do with your tuning rather than the turbo it's self.

gsracer

I don't think that is entirely true. Series 5 turbo II's don't have the twin scroll junk, and seem to do just find employing the factory boost controller.

Evil Aviator

The twin scroll 2-stage design allows the turbo to spin up faster at lower rpms. This is basically like having 2 different AR ratios on the same turbo, which results in the stock TII never going below 145 lbs-ft torque in an incredible rpm band of 1,500-7,000 rpm. Removing the 2-stage function has the same effect as increasing the AR ratio, which results in more lag but greater maximum flow potential.

See page 10 and 11 of the Mazda brochure:
http://www.aaroncake.net/RX-7/brochu....asp?Number=10
"This dual-stage operation gives the 13B Intercooled Turbo II engine unusually good response at low engine speeds."

The S5 turbo also has a twin scroll design, but it's not sequenced like the S4. The S5 turbo is what Mazda calls a "Completely Independent Twin Scroll", which is a fancy way to say that it is a divided turbo with a divided manifold. For those who don't know what this means, it is like having a "true dual exhaust" running the turbo. Anyway, this, combined with other improvements, is why the S5 turbo spools well. Simply removing the 2-stage "junk" from the S4 turbo does not magically transform your S4 13BT into a S5 13BT.
http://www.mazda.com/history/rotary/e3-1.html

banzaitoyota

Well said Evil!

Wankel7

One of you guys hit on the coating. I believe the coat is called Jethot. Also, you can use exhaust wrap on your downpipe. And if you want to go extreme they have a turbo blanket you can wrap the hot side of your turbo in. The theroy is the hotter the gas the faster they will flow. And if you put blankets on your hot baby she will stay even hotter

James

Bambam7

Just to clear up a little confusion..
It doesn't take untill 5K to build boost. I see boost at
2-2500.
I'm just saying, that at 5K, light throttle/vacuum, and I punch it, it takes about 1 second to start pulling 8 psi. Laaaag.

As for the FMIC.... they are welded together in series, with no end tanks in the middle, and the cores are 95% aligned.
Also, the IC piping is very direct, almost as short as the TMIC! This is possible due to the fact that the NA engine has it's intake on the exhaust side- doesn't have to snake around. The IC has it's input and output on the passenger side. Input on the bottom, less than 2 feet directly in front of the turbo, and the output is on the top, about 2 feet from the intake elbow! It doesn't get any more direct.

Six rotors: Yep, got the piston! Thanks for the P/N!!
Hmm.... Lysholm supercharger eh?? Muowahahahha!

Well, hopefully the sleeves will help velocity... I'll try wrapping the turbo and DP too...

gsracer

:retreats back to the corner:

Great info there. I've removed my twin scroll and while there is a noticable amount more lag I feel pretty confident that I'm making more power above 4-5k rpms with it gone. I've matched the exhuast ports evenly, and with my mbc a lot of the lag has been reduced. I admit it still doesn't not spool up as quick as with the twin scroll attached though.

White_FC

Sounds to me more like a tuning issue than the sleeves..

maxcooper

I saw a Mazda video on the twin-scroll thing once. It was designed entirely for reducing lag. Is it controlled based on RPM? If so, it might be open at 5000 RPM anyway.

Turbo engines don't have exhaust sleeves, so I don't think they would help your turbo'd NA anyway (aren't they just for noise abatement?):
http://www.mazdatrix.com/faq/6pexh.htm

-Max

Bambam7

All 13b's have sleeves. The N/A ones are very restrictive because they have a diffuser in the middle to reduce noise (that's why ported N/A's are so damn loud, that is usually removed)
13BT's still have sleeves, they just don't have the diffuser.
Without the damn sleeves, there is a huge step in the exhaust port that just isn't nessecary, it really kills flow. The manifold holes are maybe 2" in diameter at most, but the exhaust ports without the sleeves are more like 2 1/2". That's horrible for flow considering it's right on the damn engine!!! It's absence is better than having the N/A sleeve, but definately worse than the TII sleeve.
This has been dyno confirmed. There is a thread a while back on this.

To visualize what I am saying, go to the above Mazdatrix link from Max, and you can see the two types of sleeves. Now imagine that whole sleeve gone! See the size difference? It sucks.
It even states that "port flow is horrible with the sleeve out"

Suds7

Riceracing has the hugest exhaust ports ever, big exhaust ports are better for turbo cars.

von

You might reduce lag when you start boosting hiegher and get a EBC. The higher boost pressures might make up for the bigger exaust ports.

Juan

iTrader: (28)

get a small shot of nawwzZzzZZZzzZZZZZZzzZZ and turn it off when da turb0 kikz 1n OR an anti-lag system so takumi doesnt defeat you!!!!

Evil Aviator

Yes, the secondary port opens at 2,700 rpm.

Here are some ideas to reduce the lag and increase the throttle response at 5K:
1) Make sure that your AFM and throttle body are clean.
https://www.rx7club.com/forum/showth...threadid=88829
2) Install an aftermarket EMS. Porting an engine changes its vacuum signal, and your ancient 1980's technology 8bit 16k ECU and crummy AFM will not run the engine well, and I don't think that the S-AFC is going to help all that much except when it comes to keeping your engine from running lean.
3) Install a lightweight flywheel.
4) Install lightened rotors.
5) Check your clutch. Sometimes a slipping clutch is misdiagnosed as a lag or throttle response problem. If response is your primary goal, you may want to consider a 5.5" 2-disk clutch from Tilton or Quartermaster.
6) Do you have a BOV? Sometimes these will leak at vacuum if not installed correctly, which could contribute to lag when going from vacuum to boost.
7) Learn to drive the car. When racing, you should never put yourself in a position where you need to go from light throttle/vacuum to max boost. It takes a lot of extra effort to be able to drive a turbocharged car well.

Putting the cores in series doubles the core pressure drop. This means that the turbo needs to produce even more boost than it did with the stock TMIC in order to have the same boost at the manifold. This will also increase lag because the turbo will need to spool up faster to produce the extra boost. Removing the end tanks in the middle was a good idea, as this will save you from the pressure drop from 2 out of the 4 end tanks. I'm not sure if that 95% allignment sounds so good, though. You may want to consider a nice Spearco FMIC if you ever have some spare cash.

Yes it does get more direct, it's called a stock TMIC, LOL.

That depends on the application.

E6KT2

Since there is some expertise in here on this issue, I have an idea. I was going to run an intercooler behind the radiator (Not a great idea, but bear with me here) but use a vented hood and the FAL 5500cfm fan. It seems like it works for the Japanese circuit racers but I am not sure what the relationship between the radiator and the IC is on those cars. Oh yeah, the IC would be more horizontal. So the set up would be - Air in through the grill, through the radiator (I have the alluminum K2RD unit) with a BIG fan on the back. From there it would go up through the horizontal IC and out the custom vented hood.

I know the horizontal mount radiator is a good compromise, but is it acceptable to have it mounted after the radiator in the airstream?