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LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

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Old 02-11-2018, 02:45 PM   #1  
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Question Whp Guess ? Any good advice before remap

Hello US Specialists
I am from Denmark, so expect a messed up type off English
So i bought a 97 30th camaro 5,7 M6 4 weeks ago, wendesday in the following week we go into its going to the dyno for a new tune, i have a tuner guy with 12 years of experiance to help me on the dyno but not really on us cars, and i just received a JET programmer 14005, because in denmark the tunerguys havent got the right tools for most us cars.
So my
1th Question WHAT DO I MISS in my setup, or need to quick get don before dyno???

Heres my setup
completly rebuildt engine with 1500km run so far, on the rebuild it was fitted with LT4 cams and something 1,6 higher lift valve bla bla bla something, but on stock heads, New casted pistons 4,03, casted crankshaft, BBK 58mm TB, K&N cold intake, Alu Elbow inbetween TB and filter, Longtube Pacesetter race headers, dubble 3" racecats and 3" all the whey out, BBK Pulley kit, new plugs and cables oem.

What can i expect whp?

Any useful tuner infomation that we can bennefit or help us on the tuneup day, i ask because the guys that will tune it, know how to tune audi/bmw/mercedes/skylines aso, so maybe we can save time on some basics knowgles in your world.

the plan with the car is legal street race 1/8 mile
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Old 02-11-2018, 10:42 PM   #2  
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Re: Whp Guess ? Any good advice before remap

Welcome to CamaroZ28.com ! ! !

For question #1, how is the engine running now? Does it start easily, does it idle smoothly both cold and hot, does it accelerate smoothly at low throttle, and heavy throttle, any misfires, does the exhaust smell of fuel? Does the engine "surge" at low loads/part throttle? Is the "Service Engine Soon" (SES) light on? Have you scanned the PCM (computer) for codes? Has the PCM been tuned previously? Do you know the flow rating of the fuel injectors?

Are all the emissions systems still functional - exhaust gas recirculating (EGR), secondary air injection (AIR), and fuel tank vapor recovery (EVAP)? The PCM runs diagnostics to determine if these systems are functional, and if they have been deleted, the diagnostic codes that turn on the SES light have to be deleted. The after-cat O2 sensors also can set codes if deleted, but since you indicate there are dual catalytic converters, not likely someone deleted them.

As far as the modifications, let me help you out:

While you indicate "stock" heads, have they been ported by a knowledgeable LT1 Head porter to increase flow?

You indicate the pistons are 4.030” diameter, which means the cylinders have been bored, which by itself increases the displacement from 350 cubic inches to 355 ci. The displacement per cylinder has to be entered in the tune.

You indicate a cast iron crankshaft. That could be stock (3.48” stroke), or it could be an aftermarket crank, increasing displacement. Do you know if the stroke has been increased? Typical numbers would be 3.75” (383 cubic inches) or 3.875” (396 cubic inches).

Your engine only has one camshaft. And it’s not overhead, it's down in the block with pushrods and rocker arms. Sounds like you may have the LT4 HOT cam. That cam is normally run with rocker arms with a 1.6:1 rocker ratio (valve gross lift / cam lobe lift = 1.6).

With regard to the exhaust system, the header and dual cat info is clear. The question is do the headers/cats dump into a Y-pipe that merges into a single 3” intermediate pipe, to the rear of the car? Or does each header/cat feed its own separate 3” pipe to the rear of the car?

The above items have to be addresses in the tune.

The BBK throttle body has dual 58mm bores (vs. 48mm stock). The intake manifold bores need to be opened up from 52mm (stock) to 58mm to realize the benefit of the throttle body enlargement, which really isn’t necessary for a 355 ci engine with stock heads. Any small increase in air flow would be picked up by the MAF sensor.

Cold air intake change is typically picked up by the mass air flow (MAF) sensor, although it may affect MAF sensor calibration, another part of the tune.

Aluminum elbow doesn’t do much of anything.

The rear wheel horsepower estimate depends heavilly on the displacement and whether the heads have been ported

Have you (or your tuner) seen this LT1 tuning guide:

LT1 PCM Tuning - Tips & Tricks for DIY Tuning!
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Old 02-12-2018, 01:07 AM   #3  
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HI Injuneer and thanks for replying
Right now the car runs but not good, its like from +-0-30% on the TPS its "setting out" like it go to lean, so we tried to put on a wideband in the exhaust and it just write LEAN, only when 30-100% on TPS it come with some numbers over 13-15, but this we did in a driveway standing still i Neutrual so don`t know what to expect.
But when you drive it and hammer it pedal its feels good and over 4300rpm its really pulls of or spinning the rear tyres in 1-3 gear depending on road( its 0-5 degrees out side in denmark rigth now)
There is no warning light turned on in the car, there was when we tried out somethings (that day when with the wideband) but only because we diss connected the MAPsensor between elbow and airfilter, so that light worked.
i did a dignostic read on car but that was after we tried all kind of this so there was some faults, they are deleted now. But i will take the car for a ride today and read it again and see if there´s a fault.

The injectors i bellive is standard/original. I don´t think that its ever been tuned, this is a really rare car in denmark maybe 10-15 carmaros 93-02 models i bellive that i have the only M6 here! and these are tuned with filter and exhaust MAX

I bellive EGR, EVAP AIR is not disconnected, And should have been cleaned in the rebuild but this is me guessing, so maybe i have some work here before dyno/tune day the day after tommorow? O2 sensor are still there but do not know the condision of them.

I did´t rebuild the car, so i just have the invoice from the shop that did the rebuild. the cost was around 9500 of your us dollars, of them 1500 on mecanicworker hours so 8000 in parts, that is with 20% discount, don´t know if this tells you something but now you know
the Mapsensor and fuelpump are new, don´t now if fuelpump is OEM because on the invoice, its say "fuelpump diesel"
The crank is not stroked only the cylinder was redrilled
Cam i think you your right about also with ratio and lift. Heads are not ported. Exhaust is 2 x Longtube headers, 2 x 3" racecats, 2x3" all the way out with 2 x 3" Hi-flow mufflers.
Intake is looking standard to.

Yes i have seen the website PCM.. and i am now in a "translate" process of it, because its diffcult to read about programming in english for me, when i don´t have that much understanding about it but i am really trying.

so to sum up for my tuner this is what we look at: increase in volume to 355inch, incease of air flow, and exhaust flow, and the new camshaft.
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Old 02-12-2018, 09:26 AM   #4  
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Re: Whp Guess ? Any good advice before remap

The increased cylinder displacement, increased valve lift, increased cam duration, and the improved air intake system and exhaust system increase air flow. That increase is simply measured by the mass air flow sensor, and the PCM adds the required fuel.

Normally the PCM runs in mass air mode, but if the MAF sensor fails, the PCM defaults to "speed-density" mode, and calculates the mass air flow using the displacement and RPM to calculate theoretical air volume flow, and adjusts the theoretical volume flow to actual volume flow using a table in the tune called "volumetric efficiency" (VE). That's the hardest table to adjust in my mind. There is a software called VEMaster which is supposed to help. The table may be used in some other cases beside MAF sensor failure.

Minor point in your most recent post - the sensor between the air filter and the throttle body is the MAF sensor, not MAP. The manifold absolute pressure (MAP) sensor is a small black plastic rectangle on the front/top/passenger side of the intake manifold. The MAP sensor is critical because some of the tables in the tune (example - ignition timing) use MAP as a measure of engine load.

Have you found this website for reliable info on the LT1 engine, and many other aspects of the 1993-1997 Camaro:

4th Gen LT1 F-Body Tech Aids

You can download a copy of the 1996 GM factory service manual here. There are very few differences between the 1996 and 1997 models:


Given your description of the modifications, I would guess you might be around 375 HP at the flywheel, giving you about 375 x 0.87 = 326 HP at the rear wheels. You are at the practical limit of the stock fuel injectors. Watch for the A/F ratio to lean out at peak HP on the dyno. Make sure the tuner focuses on the target A/F ratio in power enrichment (PE) mode. That'important to peak HP, and is explained in the tuning document.

The big issue at part engine load is driveability.... does it surge or stumble at part load, does it transition smoothly from part load to wide open throttle? That seems to be where the experience specific to the LT1 engine comes in for the tuner.

Have you considered a “mail order" tune from someone like Solomon at lt1pcmtuning.com to get your existing tune upgraded to a more reliable baseline for your local tuner?
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Last edited by Injuneer; 02-12-2018 at 09:28 AM.
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Old 02-22-2018, 12:48 AM   #5  
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Re: Whp Guess ? Any good advice before remap

Hello again so This was My dyno result at the crank, almost 100 HP over standard pretty awesome 385,5 HP at 6354 and 479 NM at 4804 rpm
over 400 NM from 1700 rpm to 6500 rpm,
i have the dyno grah but can not upload it
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Old 02-22-2018, 09:37 AM   #6  
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Re: Whp Guess ? Any good advice before remap

Did you click on the "Go Advanced" button on the "Reply" screen? There will be a "Manage Attchments" option, with a list of acceptable file extensions. With a .jpg format, the document will show up in the post. With a .pdf format, it may show up as a link offering the reader the option to download.

I can’t remember if there is a minimum post count required before you can post an attachment.

The engine definitely has more modification than you listed. Heads have to have been ported, probably something larger than an LT4 HOT cam.

You are well over 100 HP more than stock, if those are rear wheel HP results. The stock 285 HP rating is at the flywheel, not the rear wheels. 385 rear wheel HP through a T56 drivetrain would be about 435-440 HP at the flywheel.

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