I know a lot of people switch to a single turbo set up and I know that some of the benefits are typically higher potential HP and a simpler system. I was just wondering how much lag is there in single turbo systems compared to twins. I don't think I will ever have this car be a high HP car, nothing over 400 hp and like to have a quick responsive engine.

 

Fact:
This is a very vague question, as there are a lot of single turbos out there. the GT35R and T04 series all provide quick spooling and high power applications. Also, the set up also deals with a lot of the spooling, like long or short runner, divided or undivided, etc.

If you want response, you won't get any better than the Stage 3 twin turbos.

Another benefit of single turbos, it reduces a large amount of heat that exists in the engine bay.


Unsure:
Also, the amount of lag present in a dual ball bearing versus twin turbos is basically negligible in an actual race, because it'd only be like a few rpms to reach max boost in comparison. Don't take my word for it though, I think I read that somewhere on these forums, or I could just be making the last part up, lol.

 

IMO, nothing beats the responsiveness of the sequential twins. Not to say that a single can't be responsive, but on the street or in autocross, I feel the sequential twins work best. However, 400hp is going to require a single turbo or two larger turbos.

Go to the dyno sheet page and compare dyno graphs of twin sequential, twin non-sequential, and single turbo applications.

 

Thanks for the advice, this is my daily driver and I don't really much like drag racing, but I go auto crossing every once in a while which is why response time is important to me then pure power.

 

A few things to note:

* There are single turbos today which can deliver similar performance as the stock twins
* There is a difference between a single turbo not providing full boost early and lag. A single turbo may not be providing 10 PSI at 3000 rpms, but that doesn't mean the 6-8 PSI it has at that time feels the same as 6-8 PSI on stock twins. So just don't think that because a single turbo produces full power later that you have no power in the lower rpm range. As TimeMachine mentioned, you really need to look at the dyno plots to see what's going on.

 

I am a true believer in single turbo FD's. Most of the stock setup is to be desired in many aspects. The biggest issues with the twins is reliability, complexity, and heat.

Reliability: If you start pushing them above 12-13psi, their life is drastically reduced. You will find many owners that have rebuilt or replaced the stock twins within a 100k mile span. Though an upgrade, such as BNR twins will give you longer life and more power, the OEM turbo's are still a dated design in my opinion.

Complexity: It's no secret that the factory twin design is one of the most complex created. With over 50 individual vacuum lines and many solenoids the system is pretty busy. Add 17 years of use and high engine bay temps, and things can fail quite often. There is a simplified twin diagram on the forum that does eliminate some of the mess. But to me, the benefits are fairly meek...

Heat: This is my biggest issue. Heat and rotaries don't mix,.. period. The twins generate a lot of heat. They retain much of this heat with the cast OEM manifold. Heat transfer 101 tells us that the cast steel manifold will transfer to our aluminum housings.

Going Single:

Before I state the obvious advantages, I will give the few disadvantages. The biggest is probably cost. Going single takes a fair amount of time and money. When reworking the OEM turbo system it is paramount that quality is number one. This cost includes all of the supporting system to create the desired power. A professional tune is also very important. An excellent rotary tuner is very important, and now always close to you. Do not suffice with sub par tuning. Rotaries need precision with fuel.

Single turbo's are not as laggy as you might think. There are MANY options on the market that can give you very fast spooling like the twins. As stated, your intercooler setup and piping size can affect spool. These parts, with manifold design, should correlate to your power goals and can also keep spool time very quick.

In the end, your biggest resource is research. I would recommend speaking with A-Spec tuning or other reputable shops. Look at dyno charts and turbo discussions in the Single Turbo Forum. Search, read, and learn.....

I think you will find, that going single is one of the best upgrades for an FD, with water injection in a very close second...

GL OP

 

This is the nicest spooling single set-up I have seen yet. For reference the stock sequentials are makiing a little over 200 ftlbs above 2,500rpms. Creating torque down low is what makes the twins so enjoyable to have. This non ball bearing single Gt3574 is very very close and making 217ftlbs at around 2,700 rpms while also making some great top end. If I were still running the 13b I simply copy that set-up.

https://www.rx7club.com/single-turbo-rx-7s-23/just-got-my-car-back%3B-gt3574-new-engine-887476/

 

No one really seemed to touch on what affects spooling time, etc.

 

I haven't had a lot of direct experience with FD single kits, mainly with FC kits. But, I have a few things to throw in there.

First, nothing fits and works like an engineered OEM part. The twins, for all their ills, bolt on nicely, never have problems with oil leaks or water leaks, exhaust lines up nicely, etc. Many single setups use fabbed up oil and water lines that cause long term problems, exhaust that doesn't fit quite right, wastegates that stick, etc. etc. etc.

I had a big turbo on my old FC and HATED it. Yeah, the power was nice, but it actually made the car HARDER to work on. Granted, the FC's stock turbo is about crazy easy to remove (I could remove it completely in 20 minutes). The big turbo had a V-band clamp for exhaust which I hate (they never line up the same way, use it a few times and the nut siezes up, etc.) the oil and water lines had a rigged look to them and were hard to get to, the turbo was VERY hard to remove from the manifold....I just did not like the setup at all.

Again, I don't have a lot of hands-on with FD single turbo setups. But this can be one of the few mods that makes the car HARDER to work on. Most, like a downpipe or intake, make it so much easier - no giant pre-cat in the way, no huge airbox to remove every time you work on the car, etc.

Anyhow, something to think about.

Dale

 

As stated in my previous post....

"Single turbo's are not as laggy as you might think. There are MANY options on the market that can give you very fast spooling like the twins. As stated, your intercooler setup and piping size can affect spool. These parts, with manifold design, should correlate to your power goals and can also keep spool time very quick."


Unless you are talking about turbine AR's and compressor sizing. I kind of encompassed that in turbo selection when explaining. I suppose I should have explained to the OP further.

 

lag lag blaa blaa blaa. you want response??? get a GT42R and launch that sucker at 8K rpms. there you will find all the response you want.











just joking.

 

^

 

For me a big benefit of single turbo is ease of maintenance. I can uninstall the turbo in less than 15 minutes with the twins it is a job that goes in the hours range.

It is interesting to note in the dyno plots posted in various parts how much power a car is making at a certain rpm. I find when I look at the GT35R plots their power under 4000 rpm is very nice.

 

My old Non-seq twins took the same amount of time to spool as my GT35.

Anyway, I dont get what is the big deal about turbo lag, just downshift!

 

In all fairness that is not a GT3574, elliot can call it that all he wants (and he shouldn't for obvious reasons) but it's not. 3574's come only one way from a-spec with a divided .84 housing, that's it. And no copying stuff!! Your better than that.


~S~

 

I figured as much since I started researching that turbo on the internet and came up with your web address. But I aint gonna lie, that is some really nice bottom end on that graph. As far as copying? Really not all of it! Just a couple things. I really want that turbo though(whatever it is).