Help with engine selection: F/I versus N/A

[ktm]

Before anyone says SEARCH, let me preface that I have been doing nothing but researching this very issue for hours upon hours. I must have over 30 hours of searching and reading posts on this site and I am still no further along than I was when I started.

 

I have developed the following conclusions based on all my reading:

 

1) A stock L28ET provides the most bang for the buck - that is until you decided to increase the horsepower beyond stock.

2) Building a 3.0 or 3.1L N/A stroker is relatively pricey and the gains, while impressive, are limited. Once you build it out, there is not too much more you can do to increase your horsepower.

 

Now comes my conjecture:

 

3) Building an L28ET to produce the same power as 3.1L stroker will cost just as much, if not slightly more, than building the stroker. I say this because, based on my reading, if you want to increase your power beyond stock in the L28ET, you are looking at an aftermarket fuel management software (MS), larger injectors, larger turbo, intercooler, larger fuel pump/FPR, boost controller, etc. The most significant cost is the software.

 

Ok, after saying all of this, and having a defined goal in mine of producing 200 to 220 RWHP, both options are in the running but the stroker is slightly in the lead.

 

I like turbo charged engines, especially on race gas and a cold day (thanks to my 2002 S4). However, I also like have gobs of torque on hand at low RPMs. Waiting for the turbo to spool up and hit peak book is aggravating.

 

I keep flip-flopping back and forth. I was originally set on a stroker, but then the L28ET swap kept nagging at me due to its initial low cost. However, upon further reflection (see #3), this cost difference evaporates once you try to achieve similar HP numbers (unless I am mistaken). Saying that, the sky is the limit once you get MS as far as power is concerned with the L28, so why limit yourself to 200/220.

 

This is a street car and will be driven quite frequently (not a daily driver, but I will take it into work occassionally).

 

Your sage advice is most certainly welcome.

[Tony D]

my vote would be for what I did: Turbo. 300 to 350 rwhp, daily driven to and from work in SoCal daily commuting with a blowthrough carburetted turbo system that returned 17mpg in that service. About what the car did with it's L28 and Twin SU setup....

 

With the advent of DIY EFI, and the resultant drivability enhancements that come with it, it becomes a no-brainer IMO.

 

FWIW, 220rwhp is doable without the standalone on tweaked stock stuff, but the consensus is that with the cost of MS, you may as well go with that instead of band-aiding a stock EFI system that performs with hesitation to throttle inputs compared to a MS system that responds instantly (as will most Standalones...)

[ktm]

I just remembered some more information from all of my reading. This is what happens when you read too much.

 

I recall that the stock T3 turbo is good for 12 psi and that the stock injectors are capable of flowing enough fuel up to around 250 FWHP. If these facts are true, then the only real modifications 'necessary' for the L28ET swap would be MS, boost controller, FPR and intercooler.

 

Looks like I am talking myself right into an L28ET swap. I have been trying to stay away from fuel injection as I wanted to keep the car relatively simple. I am not afraid of fuel injection, it's just that I believe carburetors are much simpler and easier to understand.

 

Thank you for your comment Tony D.

[z-ya]

The stock turbo is good for more than 12psi, and you will get a lot more torque, but the HP will be limited at around 250WHP. The T3 turbine can only flow so much, and will generate more heat than HP over 12psi. My L28ET has a stock turbo, and makes 315ft-lbs, and 250HP at the wheels. This is at 12psi. To keep the duty cycle below 80%, I have two additional turbo injectors in the IC tube before the TB.

 

The stock injectors at the stock fuel pressure are good for 250WHP (FWHP?), but that is at 100% duty cycle. To get 250WHP with the stock fuel pressure @ 80% duty cycle, you need 380cc/min injectors.

[savageskaterkid]

I can't so but so much cuz my setup hasn't been fully assembled, but the desktop dyno program says that I should be around 290hp at the crank, which IIRC is like 250 at the wheels. Seeing as a stroker setup can be expensive, you can do an L28et for pretty cheap. My first setup was a few hundred dollars, and that was all stock stuff, and it HAULED ass, till it snapped an intake stud and blew the gasket. That setup was good for like 220 at the wheels. And everything was pretty much stock turbo stuff on the N/A motor. Since I had to strip the motor again I decided to just get a Holset turbo, SRT4 intercooler, 60mm TB, and MSnS, something tells me that I'm forgetting a few parts, but all of it was relitively cheap, with the exception of MSnS which was 400, but that was assembled with the harness made for the L28et.

 

Get an N/a motor and turbo it.

[ben240z]

N/A on a good engine management with throttle bodies/slide throttle assembly(if you can find one of these) multi point injection and distributorless ignition. Beats the pants off a turbo motor in my opinion cos there is no lag. Just out and out torque ready to use. Drivable on the track and road.

[cygnusx1]

Lag is over emphasized. It's really not that big of a deal. Go turbo, hands down. The only reason people even notice the lag is because it is much, much, faster under boost. Another good reason to go with an L28ET. It is the strongest, highest flowing form of the L series motors.

[Tony D]

N/A on a good engine management with throttle bodies/slide throttle assembly(if you can find one of these) multi point injection and distributorless ignition. Beats the pants off a turbo motor in my opinion cos there is no lag. Just out and out torque ready to use. Drivable on the track and road.

 

 

Luminition Barrel Throttles make my excited....

 

But I have to agree that the term "turbo lag" is terribly misused and misunderstood. Most people, when talking about "turbo lag" are referring to "Boost Threshold", meaning the point below which a turbo will not build sufficient boost pressure. In most cases, people complaining for the turbo to "come on" are terribly mis-driving the car, and are shifting such that they are falling below the boost threshold, and have to wait for the boost to build. For instance, JeffP's car will build full boost at 3400rpm like a rocket. hit the throttle at any point above 3400rpm, and you get a car that acts like a big block Chevy with Normal Aspiration.

 

In competitive driving, when would you realistically put the car into a gear that would keep the engine below 3500 anyway? Even a 3.0L Stroker? The only place "Boost Threshold" comes into play is in first gear starting out, after that, with a properly geared and driven turbo vehicle, you (with current technology turbos) should NEVER be in a position that boost threshold ever comes into play during competitive driving once moving from a standstill.

 

Now, that being said, Jeff's engine does put out 5psi of boost from off idle (1300rpm) and at those figures his 3.0L is making somewhere well above a N/A engine's torque production at that point. The problem comes that once you hit boost threshold the startling difference in the amount of power you CAN produce is non-linear, you go from 250HP at 3300rpm, to 375HP at 3500rpm. That modulation can be problematic, especially in a vehicle with narrow hard tires... Granted Jef will usually shift his car at 7300 rpms, but he could run it out to 7500 if he so chose, but it would probably be slower as power peaks on his around 6900rpm. Similar to most stroker N/A's. Just with 2X the power...

[JMortensen]

I have yet to see a wicked fast turbo S30 that can put power down in the corners. Sorry turbo guys. I know there has to be someone out there doing it, I just haven't run across that person yet.

 

I think most people who build turbo or V8 Z cars are looking for big hp numbers and want to go straight really fast, and that's probably why I haven't run across a fast one (in anything other than a straight line) yet.

 

With the experience that I have had, I'm going from hipo L6 straight to V8 and avoiding the "lag" issues of the turbo when I eventually get to that stage in the build.

[Tony D]

I have yet to see a wicked fast turbo S30 that can put power down in the corners. Sorry turbo guys. I know there has to be someone out there doing it, I just haven't run across that person yet.

 

Paul L Neuman, #83 Electramotive Car. Wicked Fast in the corners, and used the big tires required to do so! The S30 isn't the greatest chassis for big horsepower numbers. It's not a turbo problem, it's a chassis problem.

 

I have 265's on the back, and anything less than that and they boil...

 

Turbos need big tires, if you want to use the power in a corner. Most, like you stated, are only interested in going fast in a straight line.

[JMortensen]

Comparing that car to an S30 is like comparing a Taurus to something you see in a NASCAR race. Also I thought that was an S130.

[george.bryant]

Before anyone says SEARCH, let me preface that I have been doing nothing but researching this very issue for hours upon hours. I must have over 30 hours of searching and reading posts on this site and I am still no further along than I was when I started.

 

I have developed the following conclusions based on all my reading:

 

1) A stock L28ET provides the most bang for the buck - that is until you decided to increase the horsepower beyond stock.

2) Building a 3.0 or 3.1L N/A stroker is relatively pricey and the gains, while impressive, are limited. Once you build it out, there is not too much more you can do to increase your horsepower.

 

Now comes my conjecture:

 

3) Building an L28ET to produce the same power as 3.1L stroker will cost just as much, if not slightly more, than building the stroker. I say this because, based on my reading, if you want to increase your power beyond stock in the L28ET, you are looking at an aftermarket fuel management software (MS), larger injectors, larger turbo, intercooler, larger fuel pump/FPR, boost controller, etc. The most significant cost is the software.

 

Ok, after saying all of this, and having a defined goal in mine of producing 200 to 220 RWHP, both options are in the running but the stroker is slightly in the lead.

 

I like turbo charged engines, especially on race gas and a cold day (thanks to my 2002 S4). However, I also like have gobs of torque on hand at low RPMs. Waiting for the turbo to spool up and hit peak book is aggravating.

 

I keep flip-flopping back and forth. I was originally set on a stroker, but then the L28ET swap kept nagging at me due to its initial low cost. However, upon further reflection (see #3), this cost difference evaporates once you try to achieve similar HP numbers (unless I am mistaken). Saying that, the sky is the limit once you get MS as far as power is concerned with the L28, so why limit yourself to 200/220.

 

This is a street car and will be driven quite frequently (not a daily driver, but I will take it into work occassionally).

 

Your sage advice is most certainly welcome.

 

Your title is kinda weird...:icon11:You know you can get Fuel Injected L serires motorss that are naturally aspirated?

[naviathan]

I think he meant Forced Induction (F/I)

[z-ya]

I have yet to see a wicked fast turbo S30 that can put power down in the corners. Sorry turbo guys. I know there has to be someone out there doing it, I just haven't run across that person yet.

 

Jon,

 

I pull away from cobra replica spec racers on a regular basis coming out of turn 3 at NHIS in my turbo S30. It is an up hill, off camber, 180 or so degree turn. I do have to feather the throttle to prevent wheel spin, but I am still out accellerating just about anything coming out of this turn. I'm runnning a 3.7:1 LSD, and 245-45ZR16 RA-1s all around. The cobras weigh around 1900 lbs, have 5.0L V8s, LSDs, and mega rear tires.

 

I wouldn't consider my S30 "wicked" fast (are you from Massachusetts?), but coming out of that turn, It's pretty darn fast.

[Tony D]

Comparing that car to an S30 is like comparing a Taurus to something you see in a NASCAR race. Also I thought that was an S130.

 

Oh I'm agreeing with you, my point was it's not a "turbo" issue, it's more of a "chassis" issue. Most S30 guys will not flare the body and do what is necessary to put 720HP+ to the ground. The chassis is limited on the power it can transmit to the ground with the wheelbase it has, and the stock bodylines.

 

Like Z-Ya says, if you are prudent with your turbo setup (or forced induction to be generic) in an S30, you can easily make enough horsepower to the chassis limits, and be VERY fast out of the corners. My old AutoX setup was limited to 5500-6000rpm (much like a stock L28), but would give me 17psi at 1500rpm. People expecting to have to run the r's up to 3500 to get boost were VERY suprised by the way that car came out of corners and out of the starting gate. Boiling 265's gets people's attention. But on a road course the car really pulled in the corners. I added the whaletail to be able to keep power on thorough on particular 45mph corner. After the addition of the downforce I could flatfoot it through that sweeper. I won't say it was 'wicked fast' but like Z-Ya stated, there wasn't much that stayed with me through that section of sweepers...

 

But for wicked fast I think you will need another chassis, like the S130.

 

Straight line, sure, live axle it and run 9.20's in an S30 no problem, that's old news...Japanese were doing that back in the 80's without EFI! No doubt that IS the aim of many with the S30 Turbo Camp. Just not everybody. There are S30's that can put power down in the corners, buy you are pretty much limited to >450hp to the rear wheels from what I have seen with the S30 Chassis. Don't know if that will qualify as 'wicked fast' but most S30's with 300+ N/A HP are 'damn fast' by most standards...

 

You get some people with an S30 Turbo that get interested in going around corners, I think you will see some 'damn fast' cars... I think 'wicked fast' will be limited to a more competent chassis...hence the PLN Example. You get power, you need proper preparation to put it to the ground. Yes, you will need some sort of NASCAR bracing and chassis prep.

 

I don't see that in most casual track day cars, regardless of powerplant choice.

[JMortensen]

Well you have a point. Fast is relative. I'm not saying it can't be done. Just that I haven't seen it yet, and that I wouldn't want lag or boost threshold or whatever you want to call it on my track car. I'd rather have a NA engine. Personal preference.

[Tony D]

Then I pose this question:

Why does everyone make such a big deal about "Turbo Lag" or "Boost Threshold", but the same is not done for "Cam Lag"?

**********************************************************

Most N/A engines I have see on the tracks are not putting "useful" power out below 3000rpm anyway, so you have to keep the gearing low to keep the engine "on the boil".

 

Consequently, the turbo reacts exactly the same way there is no real "useable" power below 3000rpm (though gobs more than an N/A of similar displacement)---I think the whole thing on the "lag" is just because there is so much power that comes available when on-boost when compared to an N/A coming onto the cam. Drivers able to handle the power of a turbo engine driven properly (i.e. "on the boil" like an N/A) are few and far between I think.

 

Our Bonneville L20A N/A Engine is really scary the way the power comes on up high. I would say "on-off" switch kind of reaction. But that is the price we have to pay for having the power in the RPM range we need it to pull the speeds we need to break a record. The way it pulls above 6500 is like night and day in the drive up to that point!

 

Just an interesting Anecdote: While at an instructional day at a local autox some years ago the instructor was severely talking-down turbos for the Auto-X application due to the "non linear power application" making the cars difficult to drive. It continued into the track walk, and then into the car. He was discussing this with me in-car on the starting gate (drive along instruction) as I had mentioned mine was an L28-Turbo. As we took off, he made a scatalogical exclamation, and after the run he was totally "this is a turbo??? I have to drive this!"

 

After taking three runs through the course (at a very nice speed I might add) he came back all grins, and said "I normally don't like turbo engines for Auto X, but this one I like! That thing is like a supercharged car, I can't feel the car come on boost at all, you are getting full boost below 2000rpms, no matter how I lugged it! That's amazing, it acts just like a 350V8, I can't believe that's a six in there!"

 

Key: don't get greedy, engineer for the application, and pay attention to exactly what you want to do with the chassis, and you can get a turbo seamless just like an N/A, only with bigger power. No Lag, just like an N/A, "only bigger!" LOL

[ktm]

Great, now I am back to where I started.

[twoeightythreez]

I can't wait to drive my swapped turbo S30. I did the swap over a few month's time despite my hectic schedule (I'm underway almost constantly, meaning not able to get to the car)and when inport we still have workdays.

I did everything myself and this swap cost me so far about a grand. This was including the MS kit, all the wiring stuff I needed to tie into my EFI harness, and patience.

I'm running an L28ET(with rebuilt stock turbo) I traded a $500 datsun 510 for, I paid $300 for the MSII kit and the misc. sensors, 75 for a FMIC, 50 for a 1st gen eclipse BOV, another hundred for misc. crap, and it's running right now.

I have to wait till after Xmas to actually drive the car but around the parking lot I got the full 6psi at about 2100rpm. It started spooling at 700rpm. With the open exhaust it sounds like a mack truck from 20' away.

So, dollar for dollar, if you do the work yourself, there is NO COMPARISON from this swap to a stroker. A stroker done right is gonna be WAY over a grand unless you happen to own your own machine shop.

Btw, my IC piping is cobbled together, leaks like a sieve. Once I get some good piping built (kinda hard without a bender, a welder, or a permanant residence) I'll have even less "lag".

I'll tell you what has "lag". An SR20 with a T3/T04 combo. Gutless below 3500. A buddy of mine has one, and I tell you I could OUTRUN that car to 20mph. An L28 will SMOKE an SR20DET off the line. If that's what you're comparing to when thinking of "lag" I think you'll be pleasantly surprised by the L28ET.

Yes the SR20 can output more HP on similar components, but SR20's are freakin gutless, and torque matters so much more than HP on a street car.

[twoeightythreez]

Btw, with MS you don't need a fancy RRFPR, the stock one will work fine. You don't need a wideband to tune it either. Yes a wideband will let you tune for max power but you can tune adequately with a narrowband sensor.

Cruise can be stoich or a bit leaner, and just run it a bit rich everywhere else and then just tune it over a longer period until you get max power, just like you used to do with carbs.

Plus MS will run any size injectors you want, so you can toss the stockers.

(I have 437's from 3 junked TBI 5.0 fords in mine right now. they work great)