Fast355

iTrader: (2)

Well, now that I have time to sit down and post this, here it goes. This is part 2 of this previous post.

https://www.thirdgen.org/forums/tbi/...i-project.html

About two weeks ago I finally got tired of the TINY factory cam in my 1994 L03. So last weekend, I set out to change that.

I had planned to swap in a Summit K1103 camshaft (214/224 @ .050, .442/.465" lift) but my plans changed once the intake came off. When the intake was pulled, I found that it was a factory roller cam engine. I pulled the boxed LT1 roller cam off the shelf in my garage (the same one that was in my 279 RWHP 355) and installed it 4* retarded. I changed the valve springs to much better units. While doing the springs, I noticed that the heads were 081 castings, not 187s that I had thought. I kept the 1.6:1 roller rockers on it. The factory intake went back on, along with the 1" open center TBI spacer. An Edelbrock TES exhaust system meant for a 1990 Chevy suburban went onto it as well(got them cheap from the boss).

It has had the ultimate TBI moded TBI, which I set the AFPR at 20 PSI in conjunction with the stock 55 lb/hr injectors. It started right up and ran OK, but need tuning badly. At that point, I started playing with the chip. Around Wenesday, it was running pretty good. I drove it on a 100 mile trip on Thursday and might I say, it ran pretty damn good. I set the cruise at 80 and it held it perfectly. Friday night, I stopped by my friends shop and we strapped it on the Mustang Dyno.

It pulled 258 RWHP @ 5,200 and 298 ft/lbs @ 3,900. The torque curve was flat as a table making more than 275 RWTQ from 2,000 all the way to 4,800.

RPM--------RWHP------RWTQ
1,800-------90.7----------264.3
2,000-------104.6---------274.6
2,200-------116.5---------278.1
2,400-------128.3---------280.7
2,600-------140.2---------283.4
2,800-------152.5---------286.1
3,000-------162.4---------284.3
3,200-------175.3---------287.8
3,400-------189.1---------292.2
3,600-------202.7---------295.7
3,800-------215.1---------297.3
4,000-------226.6---------297.5
4,200-------237.2---------296.6
4,400-------246.2---------293.9
4,600-------248.2---------283.4
4,800-------250.8---------274.6
5,000-------255.5---------268.4
5,200-------257.7---------259.6
5,400-------243.4---------236.7
5,600-------249.1---------234.1
5,800-------216.8---------196.3

The high RPM dip is from running the injectors static. 258 RWHP is about 303 RWHP and 55 lb/hr injectors, even at 20 PSI are only supposed to feed 290 FWHP.

Being that this is a short wheel base cargo van that weighs 500 lbs less than my 1983 conversion it is fun. Haven't had it back to the track, but it seems promising. I would not be at all suprised to get into the low 15s/high 14s with it if I gave it 3.73/4.10 gears and a 3,000 rpm stall torque converter.

BronYrAur

iTrader: (1)

Awesome numbers Fast. Those are stock unported 081's correct? That gives me a lot of hope for what kind of numbers I can put down with basically the same combo but with a ZZ4 cam. Hopefully I can hit a dyno sometime this summer, otherwise I'll get track times. Great work though, gotta love that EBL

Fast355

iTrader: (2)

As far as I know they are STOCK 081s. My uncle (the original owner) never pulled them off, nor have I. This not EBL equipped. It has the 8192 Baud TBI PCM in it.

91RockS

Fast, those are some really good numbers with an LT1 cam and 1.6 rockers. That's what I was originally planning to use with my ported 081 heads, but as you know I'm planning on a bigger cam than the LT1 (which is sitting on the shelf in my garage like yours was!). Now you've got me thinking.

Why did you install the cam at 4* retarded rather than straight up??

PS: It must really suck to have a friend with a Mustang dyno

GodOverYou

I gotta second that question. I would guess because of the relatively short valve timing, but I figured that there might be a more TBI specific reason that I'm overlooking.

Fast355

iTrader: (2)

It is due to the LT1 cam's short valve timing. 4* retard on DD2000 was worth nearly 15 FWHP @ 5,500 with no trade-off in torque @ 2,000.

GodOverYou

Well, there you have it, sounds like a no lose situation.

Fast355

iTrader: (2)

Especially considering with the stock 2,000 rpm converter in the 1994 4L60E I am at 2,000+ rpm any time the gas pedal is pushed on enough to unlock the TCC.

91ChevyRS

I'd love to put out those kinds of numbers at the wheel for my car.

I am actually gonna start saving up for some of the tuning software so I can burn my own chips. I am actually quite excited and looking forward to burning my own chips.

The only problem that I have now is my car is pretty much stock. I only have a cutout, bullet muffler, and an open element to consider me a "slightly" modded car. By the end of the month I should have all the neccessary odds and ends to burn my own chips on the car. I plan on advancing the timing to about 2 degrees, and then lower my operating temperature. The stock factory fan turns on at 220 degrees, and although I know thats my "max" point, I still think it takes a major toll on my car. My car loves being cold, and I like it to because I can actually accelerate quicker.

I have been reading up on those tuning programs though...Fast355, if you ever have the time, tell me where you started. I wanna get a new cam soon, I was thinking of just settling down for an Lt1 cam, how hard is it to tune those on our cars? And is there any big major risk to having an Lt1 cam in our car?

GodOverYou

Just keep in mind that your TBI intake likes being warm...

mw66nova

iTrader: (13)

hey fast355, i just wanted to tell you that we have almost the same combo in my buddies berlinetta. now his car has an edlebrock carb and holley intake(idle-5500rpm street dominator) and he's got a bit better headers with the hedman longtubes but they are tied into a single 2.5" exhaust(i'm building a cutout for him though, don't worry!)

he's running a stock converter and 3.23 gears, though he only weighs like 3400lbs with driver. we'll be getting track numbers in August.

hehe, it's amazing how many people are building fast 305's lately, lol! i think we may have started something!

Dewey316

Fast, those are some great numbers. Any chance you could give some information on the spark table you used? Considering the main diffrence between that and my car, is the 454 TBI unit, and the 1.6 RR's, I would like ot see how the timing compares to what I'm running.

I ended up with 34* of advance about 2500 RPM on my car.

Fast355

iTrader: (2)

Just another update from the TBI-TPI swap in this beast. The latest dyno numbers, on the same dyno. I am using a Vortec 305 PCM with a Hypertech programmer. I am running the stock MAF, 1996 LT1 throttle body, Vortec Harness, stock TPI setup, (stock 19# injectors at 60 PSI) etc. The Vortec distributer is at 0* on the scan tool.

RPM--------RWHP------RWTQ
1,800-------79.6----------232.3
2,000-------90.8----------238.5
2,200-------103.7---------247.6
2,400-------115.9---------253.6
2,600-------133.0---------268.7
2,800-------148.0---------277.6
3,000-------164.7---------288.3
3,200-------181.9---------298.5
3,400-------199.1---------307.6
3,600-------215.6---------314.5
3,800-------226.0---------312.4
4,000-------224.1---------294.3
4,200-------229.8---------287.3
4,400-------236.6---------282.4
4,600-------243.1---------277.5
4,800-------244.3---------267.3
5,000-------250.8---------263.4
5,200-------246.2---------248.7
5,400-------242.9---------236.2
5,600-------231.2---------216.8
5,800-------206.1---------186.5

5,800 is the fuel shut-off RPM in the Vortec PCM. To my knowlege nobody has broken the 5,800 rpm barrier. It is had coded into it.

IMO, this setup is better than your average TPI swap and is likely making more power than MOST other swaps. The Vortec PCM gives the advantage of Sequential Injection, Faster Processor, OBDII, Electronic Transmission Control, etc.

The Hypertech reflashed PCM seems to have adapted to this engine just fine. I need to get the stuff to do custom tuning on the Vortec engine in order to get rid of some fault codes that are coming up. It is mostly EGR, EVAP, ABS, and a few others.

The LT1 cammed, 081 headed, headered 305/4L60E/3.42 combo in a 5,000# van is getting 20 MPG highway and about 16 in town.

The TPI lost as much as 32 ft/lbs @ 1,800 RPM, but gained 17 ft/lbs peak to peak while bringing the peak TQ rpm down 200 RPM. I lost 7 HP peak to peak, but the RPM for Peak HP also dropped. To me this is an indication that the TPI intake on even a mild 305 is too restrictive. Unfortunately going to a different runner design will kill off the added mid-range torque that I put this setup on for. I can afford to lose a little torque on the bottem though as this engine is used mostly to pull 4,000+ lbs at 50-70 MPH in 3rd gear (2,600-3,500 rpm)

BMmonteSS

Very cool data, confirms ALOT of what I've assumed over the years. Thanks fast, once again you bring the tech

Edit: Added a graph of the two dyno runs layed over top of each other, it really shows how the TPI setup pumps up the torque in the power band it was designed for. Fast, what intake were you running with the TBI?

Fast355

iTrader: (2)

The stock 1994 G10 305 TBI intake with a 1" open center spacer on it.

Never thought of doing a graph in Excel or the like. Cool idea!

BMmonteSS

O'reeaaaly, very interesting indeed. Fast you really need put this in a thread of it's own titled "TPI vs. TBI....the definative awnser"

ShiftyCapone

iTrader: (7)

Awesome data indeed Fast! This is the type of stuff that us TBI guys crave. Thankfully you have more time and more resources on hand to constantly provide us with great reading material.

How did you install that cam 4° retarded? Did you use an adjustable timing chain or did you use a degree wheel and align the stock chain slightly off from straight up?

kdrolt

To add another data point to this thread, here's one of the threads on Dyno Don's testing of TBI vs TPI from several years ago:

https://www.thirdgen.org/forums/tech...ht=dad+TBI+TPI

The summary from that test is that TPI gained 17 rwhp and 70 rw ftlbs over TBI, when using the same TBI 305 long block beneath either the TPI or TBI. There were two differences worth noting that might explain some of the results.

First, the TBI was tested, IIRC from sidebar PMs with either Don or his son Kevin, in warmer weather than when the TPI was tested. I think I once estimated that the temp difference might account for approx 6 hp out of the 15.

Second, the ignition timing was set to 0 deg BTC on the TBI and 6 deg BTC on the TPI -- both factory settings. The factory sets the timing based on the burn characteristics of the factory heads (swirl port 187 casting on the TBI engine vs non-swirl port 081 casting on the TPI) and for the worst-case conditions of temp and load. Since the 187 swirl ports heads were used in both of Don's TBI and TPI tests, then the ignition timing should have been kept the same, rather than in using the factory setting. So some of the remaining 11 peak hp difference in the TPI over the TBI was due to the difference in the base ignition timing.

187 heads get 0 deg base ignition timing from the factory because they have faster-burn chambers than the 081s do. Adding ignition advance will probably add power under good conditions, but it might also lead to pinging under bad conditions/loads. The heads weren't swapped in Don's test so the timing used should have been fixed at either 0 or at 6 deg BTC. That's not a criticism of the test -- rather it's a comment to help explain some of the results.

The upshot, IMO, is that the hp difference between the TBI and TPI in Dyno Don's test was darn close to a wash. The torque difference, however, wasn't. I think I was able to reckon that approx 50 ftlb of the 70 ftlb difference was a genuine gain. And it looks like Fast355's test confirms what Don had already shown:

There isn't much of a peak hp difference in a near-stock comparison of TBI vs TPI -- and any difference might be within measurement error because the numbers are close.

and

There is a large peak torque difference between them: TPI has a big boost at mid-speeds, but loses a lot of it on the bottom end.

Dyno Don

iTrader: (7)

One point being missed in all the discussions...the total timing in both setups is the same at wide open throttle (30*) so the base timing is not relative.
After I changed to the LT1 cam and 1.6 rockers on the intake, I never went back to the dyno but did go to the track and recorded a 14.94 @ 93.xx MPH.

BMmonteSS

Don,

I read over that post, and it was stated that stock chips were ran with both combinations. If this is true I highly doubt the TBI setup had 30* of timing, most bin's that I've looked at had WOT timing in the mid to low 20's.

I think the only real difference between yours and fast's test is that fast's motor was built up a bit, and he tuned both combo's.

Dyno Don

iTrader: (7)

Well...whatever, this crap has been thrashed to death and the fact still remains, on the same motor the TPI is the better setup, regardless of how many ways it is sliced up.
Drivablity, power, looks, mileage and fuel economy...period!

BMmonteSS

It was just a question, no need to get hasty

If you care to give me the chip code from both ecm's I'll post up exactly how much timing each combo had. Even a model of vehicle, transmission, and year would be enough to track it down. But then again TPI is superior in every way so this discussion doesn't warrant any actuall tech. If you didn't notice TBI made more power every where but the midrange in Fast's test......

Fast355

iTrader: (2)

LOL. I like the looks of a TBI with an open element better than TPI. The mileage is not really any better, even with the highly accurate Mass Air, the much faster than 8192 TPI ecm (Vortec PCM), and SFI, driveabilty is not much better because it kills low-speed torque. I have never seen a low-rpm torque gain in any of the swaps I have witnessed, including my own. Peak HP was not improved and actually decreased on my swap. The TPI only bettered the TBI in a very narrow RPM band.



You were not gettting 30* of timing @ WOT. Here is a stock timing table from a L03 in a F-car. The whole table is at a -9.81* bias meaning take 10* off what you see here.



With this particular .BIN you get 18* total advance @ 3,600 rpm including PE spark. 23+5-10=18* I like to have 28* full in by 2,600 rpm for most TBI applications using good gas. The stock chip only gives 13* @ 2,600 rpm. A stock 80s carb 305/350 has as much advance off-idle as that. Attached is the timing table for my EBL setup on my current 350 TBI, worlds better than the stock timing table. Not quite as aggressive as some, but plenty agressive for me, especially when towing 4,000+ lbs.

kdrolt

The following thread is closed (locked?) but the discussions bear on the one in this thread. It was originally a "tpi or tbi better for mpg?" discussion that degenerated (in the usual way):

https://www.thirdgen.org/forums/tpi/...ter-mpgs.html?

Fast355

iTrader: (2)

Basically if you read that very long technical post, you have 2 or 3 TPI guys telling us TBI guys how bad TBI sucks and how great TPI is. Then you have 4 or 5 TBI guys who KNOW that TBI is not as bad as they chalk it up to be.

This is the 7th TPI swap that I have done, in all instances we lost low-speed torque for a gain in the midrange. My first swap was a mid 80s elcamino SS with a L-69 spec LG4 in it (E4ME Q-Jet). Second was a TBI 305 Firebird. Third was a TBI 400 in a chevy truck. Forth was a TBI 350 in a S10 Blazer. Fifth was a 1940 Chevy truck with a 383 and E4ME Q-Jet(CCC carb setup intact). Sixth was a 267 in a 1981 Camaro. 7th was my 1994 G10 with a 305 TBI (the one you are reading about)

Chadster86S10

Fast, I'm sorry to be greedy but can you tell me what biases and adders you have on that last timing table you posted? I want to try that on mine.

Fast355

iTrader: (2)

What you see is what you get on that, more or less. PE timing is zero'd out. There is a launch mode spark table that is not shown but is only in effect for about 2 seconds after a throttle punch from less than 20 mph.

I read on another thread that you are running old style non swirl port heads.

Chadster86S10

Yep! Do you think I need to add more timing to what is in that table?

RITTER

iTrader: (5)

I ran 16.6 twice in a row with my completely stock LO3 automatic 2.73 open rear(no posi)! And that was with a 1.3 second reaction time and a .9 second reaction! With them numbers and gears you're talking about I don't see why you shouldn't see low 14's !ATLEAST!!!

And I just ran that last Firday night, with my car running 220 degrees, thats where it usually runs when I idle in hot weather (don't know if that's normal) With my system in my car and all. I pulled on the scales after my first run and weighed in at 3540 lbs and with my 255/50 Kumho's that have about 30% tread life left on them.

Not trying to be a smart *** but I'm just saying it should run quicker.

BronYrAur

iTrader: (1)

I hear too many people around here saying this. You know that your reaction times are not figured in to the E.T. right? If you do, then great, but it sounds like you don't. Reaction time has nothing to do with your elapsed 1/4 mi. time.

Fast355

iTrader: (2)

You realize that the least heavy of my vehicles is 4,500 lbs, and all are aerodynamic bricks! The 423 FWHP 305 has not been run in a anything yet.

flaming-ford

iTrader: (7)

hell if i had a van as fast as yours i could scare plenty of people keep up the good work fast, i know i appreciate all the knowledge you bring to the board even though it's not f-body specific to the t anyways.

(ps. you should realy get you a gutted f-body and throw that 305 in it and show some people what a 305 and tbi can do at the track in something that is aerodynamically and weight wise compatable). I guess i'm one of the few that think your combos are insane fast for what they are.

Anyways make sure you let everyone know what your running with the new 305 once it's in.

Gunny Highway

iTrader: (1)

Why do I have the sudden urge to go out to my 350 and retard the cam????

RITTER

iTrader: (5)

No I didn't subtract my reaction times, I was just stating it. My two runs were 16.67 and 16.66 1/4 ET I posted the entire slips in the organized drag racing section under "US 131 Motorsports Park" and both those runs were without even launching, just hammering it on the green!
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I know it hasn't been run in anything yet, I was just trying to say that he should expect better times than what he was saying in his first post, thats it.