If using a different intake manifold, could the LT1 still use stock program?
 

I hope this question is suitable for this forum and I understand it is hypothetical and a rather dumb question at that. I plan to slowly explore what it is going to take to get a stock L98 TPI intake on my LT1. What is bothering me is whether or not I could still use the stock program if everything works out and this swap doesn't require cost prohibitive custom work to have done. I am assuming I am going to need a new program despite the fact that I wish to keep it pretty much stock and emissions compliant just like it would have come from the factory. So, I am not sure whether the factory program would be able to continue functioning given the clear difference between the stock intake manifold for the LT1 and a TPI intake manifold and the fluid dynamics surge of airflow from 2500 to 4500 RPM. I want to experience the intake on my engine with everything else stock so I am getting antsy about getting the intake on my car and what will have to be done. I apologize for my enthusiasm!

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Thats kind of a gray area since i dont think anyone has done this. Its more common for people with L98's to put on a LT1 intake manifold because they flow better. I am not sure how one would adapt the LT1 fuel system on the L98 intake manifold. Why are you wanting to put an L98 intake manifold on a LT1 motor?

Re: If using a different intake manifold, could the LT1 still use stock program?
 

I am not sure if it was on LS1 tech in the LT1 forum for us guys but someone claimed they did, however, they also mentioned it was for a Vortec truck so I am highly skeptical that it was indeed a successful TPI intake swap onto the LT1 when the Vortec engine has the Scoggin-Dickey base made up for a direct swap. I have spent a year asking "dumb" conversion/custom questions to try to find a simple way to get this intake onto my engine.

First off, yes, I understand the fuel rails are different in how you hook them up BUT I also notice how similar they are in a sense I might be able to get away with attaching an LT1 fuel rail on to the TPI intake base mounts. The question, however, will the fuel injectors line up correctly and how much of a difference are the bolt holes between the two? This is where I am contemplating very soon, buying a sourced LT1 intake fuel rail and test fitting it to see what this looks like. If worse comes to worse I need a custom fuel rail and the expertise of a shop since I refuse to tinker with fuel system components, I will end up torching my entire engine bay if I screw something up.

Next, there are two ways to get the L98 TPI base on to my LT1 and it is going to require a machine shop or any custom shop that can add aluminum to the base and drill new matching bolt holes so that you can actually bolt the base on to the LT1 heads. I thought about perhaps having the head mating surfaces drilled but if the LT1 bolt holes somewhat overlap the TPI base holes then it is more of a problem then a "simple" modification issue.

Why do I want the TPI intake on my LT1? I don't race the car and the only thrills I get are quick acceleration up to posted speed limits with a cushion of 5 mph over depending upon my timing with the throttle and shifter. My LT1 is a remanufactured Jasper and I am suspicious I may have other underlying problems like poor workmanship and out of tolerance components which have collectively and further degraded engine performance. My complaint, I want more torque from 2000 RPM up to where I shift, 5000 RPM, without major camshaft and head and complete engine overhauling. The TPI based on my research is perfect for my goal and with the current stock-ish configuration I am now running. Later, I plan a camshaft swap and other engine technology, part, and coating additions but for now the intake is what I want to focus on. I want more torque down low and right now you can feel that my car is under-powered for it's engine. The TPI intake should pep up the engine where I want more acceleration/torque in the RPM band I am using for my performance goals.

With all of this said, based on my assumptions, the stock program with all functioning sensors SHOULD be able to make the necessary adjustments for the new intake despite not being designed with the intake in mind. However, reading other articles online, anytime you swap a different intake onto an engine you want to have the tune to match it but the tune I am looking for is stock and keeping the air/fuel ratio for optimum combustion and emissions, no different than factory unless shops know a way to satisfy this criteria and yet improve upon performance as well. I am new to this area and I want to see if I can have this all done by the end of the summer if possible or to at least get this ball rolling for next summer.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Op..I remember your thread on swapping the LT1 intake to a TPI for the reasons you assume this would be of benefit. IIRC 99.9% of the replies were WTF, why, no, don't do it, won't work, etc.

I agree with those but regarding if a stock tune would work....well another IDK as it has never been done for...well 99.9% of the reasons why responders said don't do it.

But if you are still intent measure your AF ratio now with the appropriate software if you have it, or take it to a dyno shop that has wide band reading capabilities then do the swap and see if the AF is still in spec.

With that said IDK if the TPI intake swap would work with the LT1 TB which has TPS on it which the PCM reads and makes various adjustments in fueling, tranny line pressure, etc. Also the TB has the IAC solenoid in it which pcm uses to keep idle constant under varying engine loads (AC, PS, throttle position, etc). If the TPI TB has these sensors and they have the same output values as the LT1 TB..."maybe" there is some common parameter they both function in

Basically your TPI intake motor would need to maintain all the sensor function as the LT1 and those sensors would have to be sending the same values to the PCM as they do for the LT1 for a stock LT1 PCM to respond in the same way. Could a LT1 PCM be re-programmed....maybe. That would be a ? for a qualified tuner who would "entertain" the idea.....unless you are the one who would be wearing the tuning hat in a TBI motor you feel is what you need in your 97

Your Jasper motor is just a basic motor made with least expensive parts and machining is likely not as "rigid" as a factory or performance rebuild. Your driving style of keeping rpms low likely allowed carbon buildup faster than normal use which erodes performance and increases combustion temps. You are basically doing everything to kill power with a not so well made motor.

This will be a repeat but a cam, something more like a RV or "towing" cam would suit your goals way better than this TPI thing....IMHO

Re: If using a different intake manifold, could the LT1 still use stock program?
 

And.... the TPI intake is going to be bolted to cast iron LT1 heads because “they hold heat better”.

Get a copy of SAE Paper #920673, “New Generation Small Block V8 Engine”. This LT1 paper was written by a GM engineer, for presentation to his fellow automotive engineers at the Society of Automotive Engineers. I consider the info contained therein to be much more reliable that the stuff you've obviously been reading on the internet.

If you want good torque from 2,000-5,000 RPM, look at the HP/Torque curves comparison for the L98 and LT1 engines. The important thing here is not simply the L98’s +10 lb-ft bubble at 3,000 RPM. The important thing is the “area under the curve”, from 2,000 to 5,000 RPM. But wait.... you can't make that calculation because the curve stops at ~4,300 RPM, where the L98 falls flat on it's face. At 4,300 RPM, the L98 is making 50 to 60 LB-FT LESS TORQUE than the LT1. OK.... let’s limit the “area under the curve” analysis to 2,000-4,300 RPM. L98 still has less area under the torque curve.

From the SAE paper:

Some other info in the paper - the LT1 head intake runners had to be revised from the L98 profile to provide a smooth, increased flow from the LT1 intake runners. That would appear to indicate a TPI intake runner may not be a good match to the LT1 head intake runner. By the way, are the intake ports on LT1 heads the same shape/size as the intake ports on an L98 head?

Also shows the TPI intake to be 2.4” taller than the LT1 intake. Will that clear the 4th Gen cowl, and the windshield wiper linkage?

OK, enough negativity. Here's a source for a TPI baseplate that bolts to the LT1 heads:

https://firstfuelinjection.com/products

From this point I'll just kick back with a tub of popcorn, and watch the show.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

I have no scientific evidence or proof but having owned 2 L98 Vettes and 2 LT1 F-body’s this would be a step backwards.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

He's had a number of threads on LS1tech on the subject. He's got it in his head to spend a lot of money to go slower. Normally, I don't care what folks do with their cash, but from what I understand, he's in college and the '97 is his daily driver. He doesn't need to do anything to compromise his daily driver...needs to focus on the college grades and then worry about the serious car mods after college. Even then.....I think what he wants is wasted effort given how much it's going to cost.

If it doesn't have a catback exhaust and cold air intake yet....put them on it and drive happy until graduation.

I think the thing will run "fine" on the stock program with a different intake....but I might be wrong. I'm not sure where the idle air passages are on the L98 intake......I'm not sure if the LT1 throttle body will work with it. If it just happens to work, I think airflow will suffer badly above 4000 with a stock L98 intake. It's just a bad idea to try and do this in my opinion.

Discussions on LS1tech....
https://ls1tech.com/forums/lt1-lt4-m...d-gen-lt1.html
https://ls1tech.com/forums/lt1-lt4-m...-question.html
https://ls1tech.com/forums/lt1-lt4-m...year-lt1s.html

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Read those threads.....uh hmmm interesting reads for sure.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

A step backwards, how? Furthermore, my goal is not to make the car go faster when I have speed limits that restrict me. Instead of a rear gear swap why wouldn't the stock TPI intake give me what I seek? Sure for many it is not the best way to go about it but I guess it is my own financial risk to see what happens given no one has done this before and I wish to go there with my LT1.


So pretty much I am going to have to have a shop tune the car and be the one to install it as well since the car will be there! As I mentioned prior, this question was stupid! I plan on using my LT1 throttle body on the TPI intake though, with exceptions for the plug style on the 1991 TPI throttle body I got with my intake assembly they both seem to have throttle position sensors unless I am wrong. Maybe the EARLIER TPI engines didn't have them? However I do plan to use my LT1 throttle body on the TPI and they should be fairly interchangeable so I am not worried!

As for carbon build-up, I am using top tier gasoline and adding Gummout complete fuel system cleaner for every oil change so this issue I am having is not the problem! If my driving style was not meant for the LT1 engine then I wish to have the LT1 modified to accommodate my driving style. Enter this plan of mine to use the TPI intake.


The TPI intake is 3 inches taller than the LT1 intake. I measured them both. I have a 3 inch gap under my wiper linkage cowl to the very top of my LT1 intake. The fitment is going to be tight but we can squeeze the stock TPI intake under that cowl. Disassembly may be a mega pain if I need to ever change out the EGR valve but we shall see how things progress with this plan.

I have been given a torque curve simulation on third gen org by someone who had dyno simulation software and pretty much the torque I end up making with the LT1 at higher RPM is traded for the mid-range torque boost I am seeking. I will soon purchase that same software when I research what camshaft attributes would work best with the TPI intake on a stock LT1 and using 1.7 RRs with duration spec'd similar to my stock camshaft. That is another discussion.

You got me on the part about whether or not the TPI intake ports are matched with the LT1. I am gambling that they should be since there is not too much difference between the L98 heads and the LT1 heads with the obvious reverse-flow cooling of the LT1 heads. I am also gambling that perhaps GM may have intended to keep the TPI intake going granted how it seems like the TPI can actually be successfully swapped if modified to bolt on to the LT1 heads. I am sure GM wanted to change as little as possible between models to save on production costs and retooling here and there, no different than how the LS1 body Camaro and Firebird still used the same basic body shape of the LT1 Camaro and Firebird with the exception of the front and rear bumper covers for a case in point.

Okay so sit back and eat your popcorn. Other guys modify their engines for their driving styles and their "notion" of performance and yet for what I see to be as the more "practical" move for a daily driver to focus on my "notion" of performance for the daily drive, it is still a joke... I am willing to spend the money right now to get the ball rolling and I WILL post pictures if this project is successful.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

I don’t know this answer but will a standard cooling flow intake mate to reverse flow heads properly?

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Phoenix, there is nothing wrong with taking the road less travelled. You are certainly getting ready to do that......However, when I started "racing" my Dad told me this.....be sure to have your wallet ready. You will always be spending money. Wise words from a wise man who has walked this road before. He and his brother used to race modifieds in NASCAR back in the '60s. He said it got too expensive to stay in it. A portion of my family(my mother's side) still races in NASCAR today. The Wood Brothers. So.....racing is in my blood and it's never really crossed my mind to spend a lot of money to make a car go slower.

What you fail to see is that you already have practical. I'm just trying to get you to see that before you are out of a lot of money for very little gain. I thought you mentioned at one point money was a little tight.....am I wrong on that?

A word of caution on simulation software, they aren't perfect. Nothing against simulation software...I love what can be done with some of those packages(electrical and mechanical), but the real world can give you a hard dose of reality if you don't account for all the variables.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

The LT1 intake is dry. No coolant flows through it, so no worries there.

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Evening guys,
As an off the thought, how do the 2 motors match in the 1/8 mile which is where you are going to be running?

The only real difference in motor are manifold & minor cam specs.


Mitch

Re: If using a different intake manifold, could the LT1 still use stock program?
 

I understand your father's advice, especially with regards to racing. What I wish to do is something I feel is worth the modest financial risk to make happen.

Actually, the LT1 engine set-up I have is not quite practical enough for a bonafide daily driver that is winter driven. The Corvette/Camaro/Firebird LT1s were oriented around performance which loosely translates to racing! They are are not quite the sturdy set-up used by the Caprice/Impala/Fleetwood/Roadmaster with the cast iron cylinder heads. The heat retention properties of those iron cylinder heads lends itself to better daily driving and winter driving whereas the lighter aluminum cylinder heads are better for racing performance due to the lighter weight. The camshaft difference isn't a real problem here since the corvette and f-bodies were lighter cars than their four door siblings.

I have looked into using the B-body/D-body LT1 camshaft but the camshaft I already have for my F-body is just fine for the mix of practical daily driving and spirited driving that I do, more lift is really the issue and fixed with at most 1.7 RRs with a slight adjustment in duration to bring torque levels back down to where I want them and will use them the most! Since I don't wish to use higher numerical gearing on my rear axle as I am happy with my factory set-up, the only other option left is to make use of the fluid dynamics of the Tuned Port Injection intake which is perfect for my driving style!

So, we are now at this point and I am repeating myself for the umpteenth time on a different automotive forum. I am excited about this project because I am convinced that this intake will give me the mediocre performance adjustment that I have been wanting out of my car that is perfect for my daily driving experience and my driving style!

Re: If using a different intake manifold, could the LT1 still use stock program?
 

Based on the conversation from another forum, Stock for Stock, 1991 L98 versus 1997 LT1, the L98 will get the jump on the LT1 but nearing the end the LT1 will start gaining on the L98 since the TPI intake will now be tapped out of it's breathing abilities at higher RPM whereas the LT1 will still keep producing power into the higher RPM band.

For racing you see why everyone favors the LT1 intake over the TPI intake.