pistolpete25

What should i do as far as mods go when starting to mod a fc turbo? I was thinking of swapping the turbo for a vortech supercharger. Installing a different air to air intercooler a bigger radiator. And closing off the hood scoop to keep cooling to the max.

And before a war breaks out over turbo vs super id like to say its my preference and i wont hate on yours if you dont hate on mine. I like the linear power curve and instant boost. Even if turbos can give higher hp at top end. Were i drive im never at top end.

And what do people think of this premix fuel thing?

Sgtblue

iTrader: (16)

Stop by the stickys in the 2nd Gen. section and start reading.

RXSpeed16

iTrader: (41)

Here's the only thorough supercharging thread I've seen. IMO, not worth it, but it's your car. Do as you please.
https://www.rx7club.com/2nd-generati...-979256/page2/

Front mount intercoolers (FMIC's) are pretty common as are aluminum radiators.
I think pre-mixing helps engine longevity, but I still prefer to have an OMP and add pre-mix as "extra" protection.

Evil Aviator

The best way to go about this is to first decide your purpose for the car. For example, drag racing, autocrossing, show car, drifting, daily driver, etc. You can combine some of those as long as you realize that a combo requires compromise. Next, decide how much time and money you want to spend on the car. After making these two choices you can better decide on what to do to your car, and forum members can better help you to make that choice. For example, if you wanted to build a street car with $200 in mods and one weekend of work in your driveway, you would get very different suggestions from forum members than you would if you wanted to build a GT road race car with $150,000 in mods and 6 months of professional work.

Given your boost concerns that I will address below, it is obvious that you do not own a TurboII, nor have you ever driven a stock version of one. How do I know this? A stock TurboII has hardly any turbo lag, so it is highly unlikely that you would consider spending thousands of dollars and countless hours of work on a Vortech supercharger to solve a problem that I would equate to "The Princess and the Pea". Therefore, I would also suggest that you should try test driving a TurboII that is in good original condition so that you at least have a general idea of your baseline. In the meantime, you are asking good questions, so keep that up.

Just to make sure you fully understand the difference...
A well-matched turbo will hit its max boost in the sweet spot of the engine's torque curve. A well-matched centrifugal supercharger will not hit max boost until engine redline rpm. Many people have the misconception that a centrifugal supercharger makes a lot of low-rpm boost like a Roots or Lysholm supercharger, but this is not the case.

I'm not sure what you mean by "top end". If you mean max speed, then this is not a factor when choosing a supercharger, so don't worry about it. If you mean engine redline, then a centrifugal supercharger is probably your worst choice because it only produces max boost at redline, and therefore you would probably prefer a Roots blower, Lysholm supercharger, or turbosupercharger. A centrifugal supercharger is better suited for situations in which you want less boost at lower rpm and more boost at higher rpm, such as autocrossing.

One more thing to keep in mind is that there are currently no Vortech kits offered for the RX-7, so you would need to have a kit custom fabricated. This will not be cheap or easy, but I'm sure that other forum members would like it if you are willing to spend all that time and money to help Vortech produce a good kit for our small market.

I'm not sure why you are so defensive. Other than the infamous Ebay "leaf blowers", I can't think of any forms of forced induction that would incur any legitimate ridicule. I just want to make sure that you have the basis to make a choice that will give you the results that you are looking for, whatever that may be.

Pros: Reliable method of supplying oil to the engine if you don't trust the OMP, or if you race the car at high engine rpm and need more oil injected. Allows for clean oil injection as opposed to dirty oil injection, and allows you to use one type of oil for lubrication/cooling and another type for injection. Some people claim that it makes the engine last longer, but I have not seen any evidence of this for street cars.

Cons: Pain in the rear to add oil every time you visit the gas station, and you worry that others who may be driving your car will forget to add oil or add it incorrectly and end up damaging the engine. The fixed mixing ratio increases oil consumption, especially in 1989 and later cars, and the ratio is too rich for idle and low rpm so it tends to foul spark plugs and cause exhaust smoke. The engine does not get any injection oil at zero throttle fuel cut.

My personal opinion is to use the stock OMP system for regular street cars and save the premixing for race cars. For certain applications there are other variations, such as adding a separate oil sump for the OMP, or using the OMP system with a small amount of premix.

pistolpete25

Wow large responce. Ok the car is a daily driver. I like to have fun with my daily drivers so ill most likely be drifting a little. I have a few back roads near my place that i take my truck on for fun. There are also local street drags and i might do that sometimes. Id like to spend maybe a couple thousand doing small upgrades. Im a auto tech at a dealership so i have access to pro equipment if i need to. Or i can do stuff in my driveway.. you are correct in i dont own an rx7. But as i said i work at a dealership. 9 out 10 turbo cars ive test drove seem to lag when max throttle is applied from stop. I have already contacted vortech. Im aware i would need to custom make a bracket. Im not very knowlegeable on the forced induction systems. But isnt there a way to tune a supercharger so it hits peak at the sweet spot and releave pressure above that? And by top end i mean red line. I dont like driveing to red line ive seen the results of a relined piston engine before. I dont want that with my vehicals. I have tried to talk about systems like what is better on car talk forums and it turns into an all out bitch fit between one and the other. I didnt want that here lol. And i think ill try the premix at a very low ratio with stock oil system for a little added insurance. I normaly run a injector cleaner every 1000 miles in my truck and any vehical i own so fowling shouldnt be much of an issue. But all in all i need the car first.

Sgtblue

iTrader: (16)

I'm not a 2nd Gen. owner, but honestly my first thought on the SC system was..."why?". If you love fabbing and have deep pockets, OK...I guess. But otherwise it seems like your re-inventing the wheel on speculation. Turbos have come along way over the last several years and are proven with the rotary and FC.
I'm also with Evil Aviator on keeping the stock OMP and pre-mixing on a streeted car. Maybe with new OEM or stainless lines. When you move to a standalone ECU and can see what injector duty does during off-throttle it you'll see what he meant. Just keep your oil change intervals closer, fuel dilution and combustion contaminants tend to be a factor with the rotary. IMO neither the OMP or pre-mix are ideal by themselves. If you drive it hard, you might also want to consider an AI system to keep carbon down, along with additional cooling and knock control.

Evil Aviator

Be sure to mention this when asking build questions on this forum.

First of all, this is generally a good thing because the car would just sit there and spin the tires if the engine made 600hp at 800rpm. Secondly, a centrifugal supercharger does the same thing, only more so. In fact, this is the whole point of having a centrifugal superchager; little to no boost when in tight traffic or otherwise maneuvering at low engine rpm, and lots of boost when screaming down the straightaways. If you want to drag launch with a turbo or centrifugal supercharger, then the technique is to push in the clutch pedal, rev up the engine, and then rapidly relase the clutch. Of course, this is hard on the clutch and drivetrain, and it may immediately launch you into a telephone pole, but that is the technique nonetheless.

This is a really bad idea because the supercharger has an rpm limit, and controlling boost on the pressure side will create a lot of heat which will lower the air density and increase the chance of detonation. This is why turbos are controlled by a wastegate on the turbine rather than a pressure relief valve on the compressor.

This graphic shows a good example of typical boost profiles the different types of forced induction. I'm not sure why they made the lines the same color, but a centrifugal supercharger is on the bottom labled "Boost", the next line up is twin turbochargers (a single turbo would be similar on an RX-7), the next line up is a Lysholm (twin-screw), and the top line is a Roots. Note that this is just boost though. Later in the article you can see the power and torque differences once the supercharger belt drive power reduction and Roots blower heat is taken into account. Anyway, note that the centrifugal makes less boost than the turbos at lower rpms, and the only reason it makes a little more boost at max rpm is because the turbo wastegates are set a little too low on that test.
Ford Modular Motor Forced Induction Comparison Supercharger Dyno Results Photo 24


If you want to learn more about superchargers, I recommend the book "Supercharged!" by Corky Bell. You can order it from Amazon or other online retailers.

Rotary engines are different. Revving them on a regular basis will help keep them in top shape. If you think about it, there are no valves to float and no rods to throw. If it makes you feel better, there is a natural 1:3 gear ratio between the engine rotors and the output shaft, so the rotors are only rotating at 1/3 the rpm shown on the tachometer.

You don't need to redline the rotary engine everywhere you go, but you want to at least take it past 4,000rpm as much as possible, and reach up into the 7,000rpm range on a fairly regular basis. The FC RX-7 secondary fuel injectors don't operate until about 3,800rpm, and they will clog up if you do not use them regularly.

Injector cleaner isn't going to do jack ****, lol.

I may be able to save you some money with all of your vehicles. Go to this website and see the list of retailers who have Top Tier gasoline. This gasoline is chock full of detergents, so if you just use this on a regular basis then you will not need to buy injector cleaner additives. Note that ALL grades of Top Tier gasoline have the detergent, so contrary to the media hype, you do not need to pay extra for the premium unleaded in order to get the extra detergent. Hopefully I just saved you $100 per year.
Top Tier Gasoline

OK, so you like superchargers, you like low-end torque, and you hate revving your engines. In other words, there is nothing that you would like about an RX-7, lol. You may as well go to the MG forum and tell them that you want an MG but you hate little foreign convertibles, lol. If I had your stated preferences, I would get a bitchin Camaro with a badass Kenne Bell twin-screw supercharger.
GM Camaro Supercharger Kit

mikes88gtu

i need some help with my 88 gtu

Evil Aviator

First read the "Rules" sticky. It's really more of a guide than a set of rules.
RX7Club.com - Announcements in Forum : New Member RX-7 Technical

Then go to the New Member RX-7 Technical thread here:
New Member RX-7 Technical - RX7Club.com

Near the top left corner of the screen there is a button labeled "New Thread". Click on this button.

Type in a short title. Try to use good key words. For example, "Need Help" isn't a very good title. Something like "Air Filters" or "FC Won't Start" would be better.

Type in your text describing your question. Include the year of your RX-7 and any other pertinent information. When finished, click on the Submit New Thread button.

Don't post in other people's threads unless you have a question or comment that is related to the thread. If you are just trying to increase your post count then try to put a little thought into your posts rather than just spamming the board.

TX-7

turb?super imo

Evil Aviator

Actually, a turbo is a supercharger. "Turbo" is short for turbosupercharger. Each type of supercharger has its own advantages and disadvantages. Rotary engines tend to work very well with turbos due to their very strong exhaust stream, but other types of superchargers work well for some applications.