over the last few years I have bought 2 c4 VETTES ..one auto and one 6speed manual ...87 AUTO ..89 manual ...both convertibles...both have the gen 1 SBC TPI MOTORS ..basically chevy first serious EFI CAR WITH INJECTORS ON EVERY CLYLINDER on the 350CI motor ...WITH computer control of fuel and timing and various censors to change stuff one the fly ..either fuel or timing ...all sounds good ..
Problem is if you any thing to the motor as in mods it's a completely different set up and the stock set up is mismatched to provide good changes on the fly ..
...Let me make a statement here one thing my c4 VETTES have is basically old School distributor ..sort of ....basically distributors are one of the best tuning tools ever for engines .The ability to adjust it left or right to find the best running spot and lock it down.
So I just dove in on the c4 TPI MOTOR and told myself I will figure it out ...It became clear there was a lot wrong with the stock set up ...by today's standards the heads couldn't flow the intake also was a huge choking point also ..the cars as stock had some good torque off idle but the motors had there own rev limiter they would shut down before 5000RPM LOL
So I got better flowing heads modded to flow great ...stayed with the TPI CONCEPT of basically big torque just off idle ..got another TPI INTAKE Aftermarkit about 30 % bigger ability to flow more ...put on headers and free flowing X PIPE exhaust strait back to rear bumper in the center below licence plate ..so it can get rid of exhaust flow that the intake put in engine ..cam was bumped up on intake valve side with 1.8 rockers the exhaust side has 1.5 stock rockers ..Witch changed the cam numbers from stock ..not a lot ..in my opinion ..adjusted just where I wanted it more ...also change the injectors from the stock 22lb injectors and went with 36lbs injectors ...LOL a huge move to say the least ...
When you know nothing you have to read ..OH MY GOD ..The computer set up is nightmare of EPA INSANITY OF REGULATION BY THE STUPID EVIL FOOLGODS.
...To get a motor to operate to send signals to the computer it has to run hot so the sensors to work mostly O2 sensors are the biggest culprit ...this is counter intuitive tech .The computer tries to adjust things like ping and knock that running the motor hot enough for sensors to work basically creates ..my my my
Basically the best way to cure ping and knock is run your motor cold as you can ...being a farmer there's way more power in a motor that runs cooler ...oil is cooler ..lubes better ...heat is energy ..if motor is hot running it's power output is down ...many times I would stop my tractors idle them a bit to cool off ... If they don't cool off as they can ..it's time to figure out why ...and of course I would rest too....me and the tractors work around the clock many times as situations demanded...
Point being high torque motors worse. Enemy is heat as they put out a lot of power when the cooling system is at its lowest efficiency state ..the vette TPI MOTOR WITH ITS LONG RUNNERS. Is like velosity stacks on carbs they tend to speed the air up ..like giving a bit of natural boost ...the long runners on a c4 vette make for lower rpm power band that falls off around 4500 RPM on stock set up ..but a 30% bigger TPI SET UP moves the power up in the rpm zone ..taking a bit of torque away just off idle but extending the power zone to higher rpm ...so in the end the motor is completely different from stock ..and it computer set up with matched sensors to the stock motor ...making most of the tech stuff on working on stock motor simply useless ...like setting baseline timing with timing light and from there computer does it from there does not work to match modded motor ...just to many changes ......
One thing super good about my mods to motor is the ADJUSTIBLE fuel pressure and gauge. This is like a tuning devise I can adjust ..and the other one that c4 vette have is old school distributor witch can adjust the spark timing ..I just got done changing the distributor to a smaller cap distributor as the intake and stock distributor just can't live in the territory to tight and caused spark jumping as wires don't really hook up as they should . but now things are match up nice with new distributor
Ok problems I was facing ...motor runs way to hot for a lower RPM torque motor ....stock sensors and program can't adjust like it should on the non stock motor total mismatch ...to provide adjustment the modded motor needs for pining and knock that happens in motors that run hot ...
How to fix ...run motor cool as you can get it to run ..this will basically dam near stop pining and knock if adjusted right . computer has a SBC timing curve built into the cold start open loop the computer goes in on start up and stays there till it reaches a set warm motor mode known as closed loop ..and the computer reads sensor info and has the ability to retard or advance the timing ..it also can lenghten or shorten injector time to control fuel rate ...but none of this matches your modded motor ..
Most take there car to dyno and use a dyno to try and change things to match your modded motor ..but this really am most mission impossible now days cause not many tune these old 80s style computers that have to have a new chip burn ..plus if you could get it done it cost a fortune to have done ...
So me being the caveman tech guy ..I've figure out how to keep motor in open loop all the time and motor running cool always and adjust things in old school or caveman the tech way . As said with control of the fuel pressure and the distributor ..I am able to dial the system in
Witch all info tell you can't do with distributor . they tell you must unplug distributor from computer to adjust . Witch is crazy on a modded motor actually even a stock motor in my opinion ..obviously if your going to adjust timing by hand to a sweet spot you need all things working on the distributor ...took me about 40 minutes to find what I considered the sweet spot or dial in to lock down ..
So now the car is running like a more old school way muscle car ..I would say in reality the 36 lbs injectors are like a bit big but the car idles well at around 9-1000RPM .BUT passed idle it explodes with all it has ...
It amazing how hard it is to get EFI to work good ..and it certainly was fantastic to have the last gen one SBC style motor from the 50s mixed with the EFI C4 TUNED PORT INJECTION SET UP . Making a smart hands caveman tech guy like me able to blend in a super nice running V8 sports car with 6 speed manual trans ...hope it's been worth reading so far ...EFI NIGHTMARE GETTING TURN INTO SWEET RUNNING CAR ...BIG POWER ...AND A LOT OF USER FRIENDLY BIG ADJUSTMENTS CAPABLE ...WILL POST SOME PICS LATER ...COMMENTS AND THOUGHTS WELCOME ...
Problem is if you any thing to the motor as in mods it's a completely different set up and the stock set up is mismatched to provide good changes on the fly ..
...Let me make a statement here one thing my c4 VETTES have is basically old School distributor ..sort of ....basically distributors are one of the best tuning tools ever for engines .The ability to adjust it left or right to find the best running spot and lock it down.
So I just dove in on the c4 TPI MOTOR and told myself I will figure it out ...It became clear there was a lot wrong with the stock set up ...by today's standards the heads couldn't flow the intake also was a huge choking point also ..the cars as stock had some good torque off idle but the motors had there own rev limiter they would shut down before 5000RPM LOL
So I got better flowing heads modded to flow great ...stayed with the TPI CONCEPT of basically big torque just off idle ..got another TPI INTAKE Aftermarkit about 30 % bigger ability to flow more ...put on headers and free flowing X PIPE exhaust strait back to rear bumper in the center below licence plate ..so it can get rid of exhaust flow that the intake put in engine ..cam was bumped up on intake valve side with 1.8 rockers the exhaust side has 1.5 stock rockers ..Witch changed the cam numbers from stock ..not a lot ..in my opinion ..adjusted just where I wanted it more ...also change the injectors from the stock 22lb injectors and went with 36lbs injectors ...LOL a huge move to say the least ...
When you know nothing you have to read ..OH MY GOD ..The computer set up is nightmare of EPA INSANITY OF REGULATION BY THE STUPID EVIL FOOLGODS.
...To get a motor to operate to send signals to the computer it has to run hot so the sensors to work mostly O2 sensors are the biggest culprit ...this is counter intuitive tech .The computer tries to adjust things like ping and knock that running the motor hot enough for sensors to work basically creates ..my my my
Basically the best way to cure ping and knock is run your motor cold as you can ...being a farmer there's way more power in a motor that runs cooler ...oil is cooler ..lubes better ...heat is energy ..if motor is hot running it's power output is down ...many times I would stop my tractors idle them a bit to cool off ... If they don't cool off as they can ..it's time to figure out why ...and of course I would rest too....me and the tractors work around the clock many times as situations demanded...
Point being high torque motors worse. Enemy is heat as they put out a lot of power when the cooling system is at its lowest efficiency state ..the vette TPI MOTOR WITH ITS LONG RUNNERS. Is like velosity stacks on carbs they tend to speed the air up ..like giving a bit of natural boost ...the long runners on a c4 vette make for lower rpm power band that falls off around 4500 RPM on stock set up ..but a 30% bigger TPI SET UP moves the power up in the rpm zone ..taking a bit of torque away just off idle but extending the power zone to higher rpm ...so in the end the motor is completely different from stock ..and it computer set up with matched sensors to the stock motor ...making most of the tech stuff on working on stock motor simply useless ...like setting baseline timing with timing light and from there computer does it from there does not work to match modded motor ...just to many changes ......
One thing super good about my mods to motor is the ADJUSTIBLE fuel pressure and gauge. This is like a tuning devise I can adjust ..and the other one that c4 vette have is old school distributor witch can adjust the spark timing ..I just got done changing the distributor to a smaller cap distributor as the intake and stock distributor just can't live in the territory to tight and caused spark jumping as wires don't really hook up as they should . but now things are match up nice with new distributor
Ok problems I was facing ...motor runs way to hot for a lower RPM torque motor ....stock sensors and program can't adjust like it should on the non stock motor total mismatch ...to provide adjustment the modded motor needs for pining and knock that happens in motors that run hot ...
How to fix ...run motor cool as you can get it to run ..this will basically dam near stop pining and knock if adjusted right . computer has a SBC timing curve built into the cold start open loop the computer goes in on start up and stays there till it reaches a set warm motor mode known as closed loop ..and the computer reads sensor info and has the ability to retard or advance the timing ..it also can lenghten or shorten injector time to control fuel rate ...but none of this matches your modded motor ..
Most take there car to dyno and use a dyno to try and change things to match your modded motor ..but this really am most mission impossible now days cause not many tune these old 80s style computers that have to have a new chip burn ..plus if you could get it done it cost a fortune to have done ...
So me being the caveman tech guy ..I've figure out how to keep motor in open loop all the time and motor running cool always and adjust things in old school or caveman the tech way . As said with control of the fuel pressure and the distributor ..I am able to dial the system in
Witch all info tell you can't do with distributor . they tell you must unplug distributor from computer to adjust . Witch is crazy on a modded motor actually even a stock motor in my opinion ..obviously if your going to adjust timing by hand to a sweet spot you need all things working on the distributor ...took me about 40 minutes to find what I considered the sweet spot or dial in to lock down ..
So now the car is running like a more old school way muscle car ..I would say in reality the 36 lbs injectors are like a bit big but the car idles well at around 9-1000RPM .BUT passed idle it explodes with all it has ...
It amazing how hard it is to get EFI to work good ..and it certainly was fantastic to have the last gen one SBC style motor from the 50s mixed with the EFI C4 TUNED PORT INJECTION SET UP . Making a smart hands caveman tech guy like me able to blend in a super nice running V8 sports car with 6 speed manual trans ...hope it's been worth reading so far ...EFI NIGHTMARE GETTING TURN INTO SWEET RUNNING CAR ...BIG POWER ...AND A LOT OF USER FRIENDLY BIG ADJUSTMENTS CAPABLE ...WILL POST SOME PICS LATER ...COMMENTS AND THOUGHTS WELCOME ...
