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Tuning Stock 3.0L

3K views 12 replies 7 participants last post by  Ondonti 
#1 ·
I am trying to find out if there is any way to tune the completely stock 3.0L V6 (specifically in a manual '91 Daytona) without any kind of aftermarket parts. Like adjusting fuel pressure, timing, tricking sensors to "correct" for "bad" air/fuel ratios, etc. So far I've found nothing at all. Anyone have some advice for me? Just looking to see what can be improved on within the constraints of a stock engine, ECU, and fuel system.
 
#3 ·
I really want to keep the car as close to 100% original as I can because the car has loads of sentimental value. I really don't have the time, money or space to modify anything anyways, so just messing with stuff that can be adjusted is all I can do. Plus, apartment complexes don't exactly see old cars with open hoods as desirable...
 
#5 ·
I do not want you to waste time/money and become frustrated so here is my story...

My Son did absolutely everything to his 3.0L and the car ran slower, he went from 16.10 in the 1320' to running 16.80 in the 1320',
He like me was a Bracket Racer,his original goal was to get into the 15's so he could run two classes at Atco Raceway (Pro 15.99 cut and Street 12.00 and up)

After witnessing him spend hours and hours and tons of $$$ over a three year period for nothing but aggravation and frustration I am not a fan of "Attempting To Mod/Tune a 3.0L".

The mods were not done all at once, the exhaust was on there when he was running 16.10 and as he added mods such as the ported plenums he got slower, the more he did the slower he got.
He had the plenum and intake ported, added spacers, had the heads ported with a 3 angle valve cut and had the manifolds/spacers/gaskets port matched to the head, installed a 3.8L Mini Van TB, Cold Air Intake (real cold air, plumbed to the opening where removed fog lamps were), 3" Exhaust with Low Restriction Cat and Muffler (got ticketed twice for excessive noise) and work done on the A604 (shift kit, heavy duty clutches, final drive gears from a mini van, torque converter), installed a manual fan switch to keep the engine at a lower temp when racing (he experimented with different temps), installed a trans temp gauge, auxiliary trans cooler, etc and a Wideband O2 Sensor (the car was running about 11.5/1 @ WOT (You cannot install an Adjustable FPR without modifications to the Fuel Rail), Street Slicks and Air Bags in the rear to prevent squatting on launch which unloads the front wheels.
It made absolutely no difference if he shifted or let it shift on its own.

On a couple of occasions I verified the basics for him just to be sure they were correct...
Compression/Cylinder Leak Down, Fuel Pressure, Injector Flow, Map Sensor Response and Ignition Timing at all RPM/Load Conditions, wish my 2.2L was as sound as his 3.0L.

So, thats my 3.0L experience/story, take it for what it is worth.
Others will tell you that the 3.0L mods work to improve performance but you cannot prove it by me.

FYI..
Giving suggestions on what may or may not have been wrong with his setup is now a MOOT POINT since he sold the car a year ago with all types of additional parts for $500.00
 
#11 · (Edited)
I do not want you to waste time/money and become frustrated so here is my story...

My Son did absolutely everything to his 3.0L and the car ran slower, he went from 16.10 in the 1320' to running 16.80 in the 1320',
He like me was a Bracket Racer,his original goal was to get into the 15's so he could run two classes at Atco Raceway (Pro 15.99 cut and Street 12.00 and up)

After witnessing him spend hours and hours and tons of $$$ over a three year period for nothing but aggravation and frustration I am not a fan of "Attempting To Mod/Tune a 3.0L".

The mods were not done all at once, the exhaust was on there when he was running 16.10 and as he added mods such as the ported plenums he got slower, the more he did the slower he got.
He had the plenum and intake ported, added spacers, had the heads ported with a 3 angle valve cut and had the manifolds/spacers/gaskets port matched to the head, installed a 3.8L Mini Van TB, Cold Air Intake (real cold air, plumbed to the opening where removed fog lamps were), 3" Exhaust with Low Restriction Cat and Muffler (got ticketed twice for excessive noise) and work done on the A604 (shift kit, heavy duty clutches, final drive gears from a mini van, torque converter), installed a manual fan switch to keep the engine at a lower temp when racing (he experimented with different temps), installed a trans temp gauge, auxiliary trans cooler, etc and a Wideband O2 Sensor (the car was running about 11.5/1 @ WOT (You cannot install an Adjustable FPR without modifications to the Fuel Rail), Street Slicks and Air Bags in the rear to prevent squatting on launch which unloads the front wheels.
It made absolutely no difference if he shifted or let it shift on its own.

On a couple of occasions I verified the basics for him just to be sure they were correct...
Compression/Cylinder Leak Down, Fuel Pressure, Injector Flow, Map Sensor Response and Ignition Timing at all RPM/Load Conditions, wish my 2.2L was as sound as his 3.0L.

So, thats my 3.0L experience/story, take it for what it is worth.
Others will tell you that the 3.0L mods work to improve performance but you cannot prove it by me.

FYI..
Giving suggestions on what may or may not have been wrong with his setup is now a MOOT POINT since he sold the car a year ago with all types of additional parts for $500.00
One issue i see is that with an NA car your WOT was hella rich and that drowns out performance as well. For an NA car at WOT your AFR should be between 12.5-13.0 to be safe and readjusted if it goes over 13.3 at WOT.

11.5 is closer to boosted application. Should have tried to lean out closer to 12.5 AFRs. My ST ran in the 10.5 to 10.9 AFR at WOT.
 
#6 ·
final drive gears from a mini van

Right here is the cause of his car getting slower. The minivans ran longer ratios, which would have made the car slower no matter how much power he gained. If he wanted quicker he should have went with shorter ratios from something like a Neon. Once he installed the minivan final drive, any other mods were moot.
 
#7 ·
Actually that is not true.
He slowed down long before he changed the final drive gears, they and other trans mods were the last resort.
He only changed the gears to see if it made any difference.
He had the trans out and swapped in Final Drive Gears from a couple of different compatible cars to see what would happen and none including the OE Gears made a difference.

He had the trans apart so many times he was able to complete the entire procedure in only a couple of hours (including R+I the trans) and he also had technical help from a 30 Year Chrysler Transmission Tech (not me).

Until I actually see in person at the track a Chrysler 3.0L running quicker than 16.00 consistently even in 90 degree high humidity conditions without an added turbo/NOS/Manual Trans/Aftermarket Ignition/MegaSquirt, etc then I will continue to say it cannot be done.
 
#13 ·
I'm pretty sure my friend helped with diagnosis of this car, and not all advice was taken regarding the most basic things.

A factory 3.0 gains power by adding airflow, adding NO FUEL, which leans out the mixture and gains HP. Added timing is great but 20 years later I don't know what the a604 thinks of that. My wife's stock 3.0 a670 knocked with timing bumped above stock.

The a604 is not friendly but my Spirit with a604 ran 15.4@88mph with less modifications and junkyard tires. its not going to go half a second slower because the temp warms up. The ECU doesn't even have an intake temp sensor.
I've had my gutted race car Junkyard down the track on slicks with no turbo, and it ran a 15.4 also. That doesn't make sense unless you know the cylinder heads had leaking valves and it was down on power. I had stolen parts from the car and put junk heads on to move the car around. You couldn't really tell the motor was sick unless you did a leakdown on each cylinder.
 
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