I am new to the single turbo scene having just sold my fd ( had sequential bnr's ). The new fd has a gt35r. One thing is obvious...The response time or turbo lag. What was once an instant response feels like an eternity on a single. I'm slightly exaggerating that

There are so many turbos and then a pile of options for each. To say I am confused is an understatement.

While I try to decide if the current turbo is right for me I would like to know the following.....

1) More boost = better response? I've read posts where people said they got better response because they went from 15lbs to 18lbs. What was lacking was how much of an improvement it made. Is it noticeable, or is it 100-200rpms?

2) Is it common for cars to peak at a certain boost level then fall lower as the rpm's go higher? Say it peaked at 15lbs but tapered down to 12lbs as it approached redline. I know of a few cars that have that issue, and one of them is mine!

3) Possible reasons why boost might fall. Besides, boost controller, wastegate, and leaks...

4) This might be the wrong section but does water injection preturbo speed up response and if so is it again noticeable?

5) My current car is extremely quite, considering the mods. Would removing the cat make a significant different in response ( I just asked this question in another thread but I shouldn't have hijacked the post ).

You might guess by now that I'd like to have quicker response. I know I will never have the same response as the twins had but every bit might help close the gap.

Thanks for your help guys, and any advice you have is greatly appreciated.

 

Do you know the a/r on the exhaust turbine. Changing to a smaller size would help. Also I dont think those hks manifold flow that well.

 

When are you seeing positive boost, full boost? What boos are you running? Is the cat on there stock or high flow? Removing restriction from the exhaust will certainly help boost response.

 

Tapering boost as the rpms climbs high usually means restriction, intake, exhaust, turbine a/r etc.

Pre compressor injection will slow down response, tracked it on the dyno myself.

Removing the cat will make a BIG difference in spool and top end power. Turbine wheels also work on a pressure differention, the lower the post turbine backpressure( exhaust system) the better.

 

I took it out for a drive yesterday. In 4th gear I started around 2500 RPM, and it hit 1 bar around 4300-4500RPM. Boost peaked at 1.1 bar, and by 7000 RPM, boost was down to around .85-.90 bar To me this seems a bit slow for a 35r.

My exhaust has a cat, resonator, and the WG is plumbed back in to the DP.

 

remove the cat and keep the resonator, it will spool quite a bit faster, and boost will not drop off as bad.

which manifold are you using? what EMS, how is the timing set up, timing has an enormous effect on spool (not to mention power, and longevity)

cheers

kenn

 

The kit was purchased at the RX7 store, and I am using a PFC. Unfortunately I am not sure a bout the timing

 

I believe I originally installed that kit. Its Charns old FD correct?

The cat has to go for sure! Its probably causing huge backpressure in the exhaust and killing the turbo's performance in the higher RPM range.

Also tuning tuning tuning.....ignition timing has a huge effect of turbo spool and response.
That Veilside FD we just tuned, picked up 20HP and made the turbo spool much quicker and smoother by adjusting timing.

 

Sorry for the late reply. Yes it is Charn's old car.

I understand the cat could be at fault. I am also going to assume the tune is ideal since Marco did it.

I am frustrated with this turbo, and I am at a point where I am debating on just replacing the entire setup. I want something faster than 4400RPM, and more on the top end too. Could removing that cat be enough I doubt it, but I dunno.

I have been reading, reading reading. If I do change the setup, I am thinking of the precision PT67H, or A spec 500r. Some members have claimed to get boost under 4k, and make a ton more power than the 35R. Quicker response, and more power..... Any suggestions?

 

I looked back through Charns old logs and have a better idea of what it was doing now. I made a graph of it... it was hitting 1 bar by roughly 4800 RPM. I remember now I told Charn it was way laggier then it should have been and the boost was trailing off once it hit peak. We were going to try the stiffer wastegate spring but Charn being a lawyer was busy and we never got around to it. While it may be helping, I still think its the cat that is being restrictive. It's almost boost like a 42R LOL.

Take note jumping to a 500R-SP or any 67mm turbo is a big jump. Your not going to get more response from a bigger turbo so unless you find out why its spooling late and fix that with a turbo upgrade, its only gonna get worse.

I wonder if the turbine / turbine housing is ok? He did blow his old motor on that turbo if I remember right. Maybe pull it off and have a look?



thewird

 

Thanks for the chart. It looks very similar to what I saw when I was driving it or as well as I could see trying to watch the road, and the commander

I was under the impression that his motor appeared as if sand was poured in to it ( and yes that is very hard to explain ). I do have the stiffer wastegate spring he gave me. I will pop off the turbo, take a look, get the cat yanked out, put in the other spring and see where that takes me. I am just annoyed and wanted to replace it all, however that seems foolish.

As for the other turbos spooling slower, I was just banking on the fact that this turbo/setup is not the best, and had I got a better manifold, a divided housing and all that I might kill two birds with one stone.

 

You could get a Precision Billet 6765 kit with a 0.84 divided turbine housing for response for $3440 from A-Spec. Or you could try those new EFR turbo's which are supposedly much more responsive due to the lighter turbine wheel (with an external wastegate so there is no surprises later that the internal gate can't hold low boost).

thewird

 

If that turbo kit was a one of ours it's probably on our old manifold. Not the most ideal manifold out there but we got full boost by 3800 rpm. I would put in the stiffer spring and lose the cat and see how it does. No need to buy a new setup if you can get that spool down. The manifolds we currently use in our kits is divided and a lot nicer than the old ones.

 

If it is an RX7 Store GT35r kit I wouldnt think the exhaust manifold was an HKS one? Jason could tell, but I dont think it was an HKS, but the early ones it could be I dont know.

Is your GT35r a dual ball bearing model? That makes a big difference.

Oh yeah, your exhaust..... Well, w/the twins and therefore especially w/a single a totally free flow exhaust is the way to go. I know that w/twins, downpipe, and a cat back while retaining the cat will make the twins housing glow red. That glow has got to go! My exhaust: 3" downpipe then 3" to 4.5" to straight shot flow muffler w/5" tip.

Also, I am running a GT35r kit from the RX7 Store and my car has virtually no lag. I can easily get 20lbs. boost in the high 3ooo's w/no lag. If your fd has a very well built engine, and all the goodies, the only thing you should be worried about is how to keep it straight before you get it going fast.

You need to talk to Jason and give him all the info on your car. Sounds like you are actually having the most fun you can have w/an fd. Learning, tuning, and cruising. Thats what its all about and when done right the fd is hard to beat for the money.

By the way, I was hesitant to go single for years because I was afraid of the response time and low rpm power. However, even though my car was very quick w/twins it couldnt think of outrunning my current setup. Night & day bro.

 

I forgot to mention my wastegate is a Synapse 50mm. I am currently using the stiffer spring w/the smaller seat. I use port D but I know lots of guys use 2 nips on wastegate y'd to one vac line. I like to use D. I see boost levels in the low to mid 20's fairly regular but only for a few seconds at a time. My TruBoost boost controller will only hold it down so much do to the extremely well built engine.

Get it goin straight before you get it goin fast.....