Forced Induction - What did I do?

Well I went from a stock 356 engine to a 408 iron block with all forged internals and about a 9-1 compression. Went from the 3.125 pully on the SC to a 2.5. Now I get no power out of the car! It will get about 7# boost and no more and there is no power there. So did I just build the engine to big for the SC? My husband is not going to be happy! Any ideas what I can do?
Thanks

What kind of blower is it??? you can have to small of a sc for a motor but you should still see some kind of power gain from it... Has it been tuned?? Do you know the AFR?? What kind of power is "no power" ???

It is a Vortech V9 system with the aftercooler. Texas Speed told me the engine should put down about 430 just by itself. We can't even get it to 400!!! It is at the tune shop right now. They are great I just don't know if I did something wrong! I can't figure out why it can't get any power. THe SC seems to platue at 7# around 5000 and wont go up!
I went from a 550HP 356 to a 348HP 408! Not a good thing!!!

What kind of blower is it??? you can have to small of a sc for a motor but you should still see some kind of power gain from it... Has it been tuned?? Do you know the AFR?? What kind of power is "no power" ???

It sounds like she's having the same problem as you Chris, she put on the blower and is still slow.

That's cuz I broke my tranny you as$ :( Soon she'll be back up and running stronger than ever...Then something else with break... :jest:

That sounds kind of weird that it would honestly choke it down that much... Is everything installed properly??? Is the filter clogged totally??? Hmmm, many many variables to consider.... Good luck..I know how hard you've worked on this and I hope that you get it back up and running for your husband... :drive:

Well thanks, I doubt that will happen because he is coming home in 2 days! I have spent so many down days waiting for parts that are supposed to help but it seems don't! As far as I know everything is installed correctly, it is getting enough fuel, they had the guage monitoring that on today. It runs! I am just baffled by WHY it won't get any power! air filter is clean and EVERYTHING is new!
I have resigned myself to dissapointing my husband, I took in some of the body pannels to have some scratches fixed and the guy ended up messing the car up worse! It looks like CRAP now! I have to get it fixed from getting it fixed! I wanted to redeem myself with a killer engine but it apears I have done something to loose HP? I don't know what more can be done! I can't afford anything else!
I will keep you all posted. Any more ideas would be great.

Make sure there is plenty of fuel and air getting to the engine. There really is to many variables to really say what might be wrong. You should talk to the engine builder and get their opinion. What was the compression on the old motor?

I feel maybe I should take the SC off and see where it is at without it and go from there, at least it should get more HP that way!

You guys should come down to OC and check it out!

Surely... Where in the OC are you???

That's actually not a bad idea... That would see if the blower has become that much of a restriction...Remember it's designed for a stock cubed engine...You're going to have to get it tuned for a NA mode though...

It could be belt slip on the SC.... especiallly with the plateau that you describe.

One more question...Is the crank pinned?? Like Frost said it could be slipping quite a bit...

They checked belt slipage and it is not. The 3.125 pully was putting out 4# boost. On the origional cub engine it put out 9#. So I went with a 2.5 pully to get more boost.
The car is at Orange County Corvette right now on the dyno. THey are blocking of the blow off valve to see if it was leaking, but on the last run it blew off the throttle tube! so that to me indicates it has boost. I wanted to have it done today so I can bring it home to detail it but I am thinking that is not going to happen. I need to make sure it is getting the HP it should be though.
GRRRRR!!!

Yes crank is pinned, I pinned it myself! I did most all the assembly myself short of the rotating assembly. I even have pictures!

Holy shit you sound like the best wife EVER :jest:

Don't beat yourself up; I'm sure that this will work itself out. Do you know what the max CFM of that blower is?

I don't know about the CFM on the SC.
I just got off the phone with them and they found oil behind the crank pulley. So they are checking the seal and everything. THey are checking the bolt and everything to make sure it is good. Maybe the crank bolt loosened! Lets hope! I am getting rather frustrated right now! I only have 2 more days to get this done!

Yes crank is pinned, I pinned it myself! I did most all the assembly myself short of the rotating assembly. I even have pictures!

Want to trade husbands? You can have me, and your husband can have my wife. She knows how to cook, iron, and use credit cards. Sounds like a fair trade :) Can't help you with the blower issue though :P

I will say this much though, if I came home and found my Wife tried to get the paint fixed on my car, as well as having a new motor built for it, even if there were some kinks to be ironed out I'd be happier than a pig in shit!

Well I am not very good at keeping the house cleaned or ironing the clothes, sometimes I can cook good but I don't have a ton of time! If your motorcycle needs to be set up for the track or your car needs fixin I am your gal! I built the engine myself! I had Texas Speed assemble the short block (pistons and crank and machine the block) I did everything else! Took the old engine out, put the new engine in and even have the old covers and pulley and misc other parts powdercoated to match the Collectors edition black and yellow paint scheme!

oh you may confused since someone else is working on it right now! I took it to Orange County Corvettes to have it turned on for the first time and have it tuned and broke in on the dyno. They are really great! They are making sure it is done right and I am happy for that I just hope it doesn't have more problems then I can fix!
Here is a picture of the SC

The G-Trim blower is good for ~825cfm.

So honestly what is my SC kit worth? If I remove it and go with something else what can I expect to get for the whole kit? I am really bummed right now.

Hey SS1
in your sig it says you have the G-trim but will soon be a T-trim. What is this and is it bigger? Will it fit under the hood? What kind of price are we looking? I am trying to figure what to do.

I asked a question about blower sizes on here a couple of weeks ago. The general consensus was that a blower will support X amount of CFM, and the horsepower it will support is proportional to the CFM (~1.5cfm per HP).

I don't see why you can't get the same peak horsepower out of a 408 that you got out of a 346, with less boost. Something isn't adding up, so don't give up on the G-Trim yet.

FYI: The T-Trim is a larger Vortech blower that will flow ~1200cfm. You can replace the G-Trim with a T-Trim, but it will require different brackets. There is a company called RMCR Performance (not a sponsor) who sells the entire upgrade kit for just under $4000. I believe their kit is the one most of us with the T-trim are using. I think Speed Inc. also has a T-Trim bracket for our cars.

That little 800cfm blower can't really feed a 408 very well. I briefly had a g-trim on with a 418 and a 2.75 pulley. It made 5#'s and you could barely feel the boost. Now the t-trim on the other hand made 12#'s and the boost effect was quite noticeable. I'd just step up to the YSi and call it a day.

well unless my G-trim is worth something close to that I can't afford it! I spent all my savings on the engine and everything I did for the car already! Can you hook it up with the rest of the system? just change out the blower and keep the same crank pulley and aftercooler and all that? Just a new bracket and new blower? Thanks for the info, anybody have one they want to sell me for a GOOD price? I have to sell my other one first though! Oh and any hood clearance issues?

Im guessing its gonna be something simple that you just havent noticed yet. You getting spark in all the cylinders? What kinda plugs did you use? What did you gap them too? All the coils plugged in, all the injecxtors plugged in and pulsing? Hows the fuel pressure?


If your seeing 7PSI and only getting 350RWHP something is very wrong. That blower is not a restriction if you are getting boost. There a rag stuck in theintake? :jest:

I don't know if this helps but if I came home from a trip and found that my wife put in a killer motor and and fixed the paint on my car, I wouldn't give a damn if it made 2 horsepower and looked like herbie the love bug, I would be the happiest man on Earth!

Well, maybe not if it looked like herbie.

Down power can be a one of a million bugs on a new motor. Maybe the cam is off a tooth? Leaking boost somewhere (misaligned gasket?) plug electrode bent down? Low battery causing weak spark? Bad gas? I list these because I've beat my head against the wall before for each of them. ;)

Good luck with it and let us all know how it goes!

Well I am not very good at keeping the house cleaned or ironing the clothes, sometimes I can cook good but I don't have a ton of time! If your motorcycle needs to be set up for the track or your car needs fixin I am your gal! I built the engine myself! I had Texas Speed assemble the short block (pistons and crank and machine the block) I did everything else! Took the old engine out, put the new engine in and even have the old covers and pulley and misc other parts powdercoated to match the Collectors edition black and yellow paint scheme!

I wouldnt sweat it too much, if any of our wives were 10% as cool/nice as you wed be living in a dream world. Even if you dont get it all done in time all that time and effort will be obvious and will be greatly appreciated. Heck you can work on it together if its not done in time.

So relax, take a break, have your sister come post on here if shes single etc etc. :jest:

Valve springs?

In the pic of the engine it still has the stock fuel rails and regulator. Drop in fuel pressure maybe? Injectors too small? Should be able to see it on the wideband though. Just a thought. Make sure they set up the new displacement in the computer for the larger engine.

+1, don't worry if its not complete, he'll be happy.

I think she had a dual Racetronix intank setup done by Lonnies.

I have NGK Tr6 spark plugs gapped to whatever they need to be, lonnie set up the racetronics dual pump set up for me and I know it is working. They had a fuel pressure guage on the car for a little bit to check. injectors are FAST 55# and I think they were at 80% I am going to head over there in about an hour and 1/2 I will take the computer and keep in touch. I will check all the things mentioned and see what we see. You are right something is amiss if the car is running this bad, I just hope it is something stupid easy!

I have NGK Tr6 spark plugs gapped to whatever they need to be, lonnie set up the racetronics dual pump set up for me and I know it is working. They had a fuel pressure guage on the car for a little bit to check. injectors are FAST 55# and I think they were at 80% I am going to head over there in about an hour and 1/2 I will take the computer and keep in touch. I will check all the things mentioned and see what we see. You are right something is amiss if the car is running this bad, I just hope it is something stupid easy!

55# inj's at 80% duty cycle, and making <400HP??
I'd be REAL curious as to where all that fuel is going.. :bang:
FAST injs are rated at 55# @ 3 bars. If so, at 58psi, that's a TON of fuel at 80%!! :eek2:

55# inj's at 80% duty cycle, and making <400HP??
I'd be REAL curious as to where all that fuel is going.. :bang:
FAST injs are rated at 55# @ 3 bars. If so, at 58psi, that's a TON of fuel at 80%!! :eek2:


Thats what I was thinking....

Are these guys any good at tuning? Not trying to be a smart ass, I've just never heard of them. It makes sense that you're making less boost, thats obvious, but something is seriously wrong if your "using" all that fuel but not making any power.

that blower should be good for 550rwhp, a few folks here have done it already.

This sounds a lot like my car when I ran on the dyno and in stead of 400hp I only made 290hp. What we found out was that the computer decided to dump fuel in to the motor and it just killed it. If its getting way to much fuel then that could be the problem.

Is this the same dyno that it was dyno'd on before???

No this is not the same shop that did it before. THEY broke my car before because they didn't bother to monitor the AFR!
These guys are helping me A TON! I appreciate them, they are making sure it is done right! I HIGHLY recomend them! I know this will get worked out I just hope it is in time!
I will ask about the fuel. I did ask the tech again to make sure I gave the correct info and he said the injectors were at 80-81% duty cycle. They were debating over it yesterday about where they max out and such so I know it was high duty cycle.
I checked the coil packs, the battery is new, I will check the plugs, we did find the crank bolt was not in tight enough so that may be something. We shall see what happens.
A few more hours and I should have some more info.
Thanks for the help and the concern! I will keep you posted.
OH AND I am changing the mobil 1 out! They put it in yesterday and I didn't really say much but I am putting my foot down now! It is my car and I want non synthetic oil in it for a few thousand miles! I got the rotella t and am changing the oil right now!

I don't know about a few thousand miles but I would recommend for at least 500 miles to make sure that the rings seal properly... The funny thing is that I think I remember that Corvettes have Synthetic oil in from 0 miles and on...Then again they're not going to be pushing 700-800rwhp with it...Either way it seems like you definitely know your stuff and just keep going in the right direction...Usually it's the most obvious thing that's been staring you right in the face...

I'm not sure if this was mentioned earlier but I'm to lazy to go back and read, what is the AFR at and did you have a chance to pull a spark plug and check it out? If your making the boost, getting spark and fuel the power should be there :bang: No codes are comming up, misfire ect? You may want to have who ever is doing the tunning to check there wide band and make sure its reading accurate because who knows maybe its running rich.

Also is there any blowby?? Any smoke of any color coming out of the tailpipe?? Something has to be going really wrong for it to be dynoing sooooo low....

Also is there any blowby?? Any smoke of any color coming out of the tailpipe?? Something has to be going really wrong for it to be dynoing sooooo low....

Checking the plugs might indicate blowby and if shes running rich/lean.

I hope you figure out the issues good luck :drive:

Id deffinatly change the oil and see if it smells like gas. Maybe its dumping tons of gas and its just leaking down intothe crankcase. Which would suck especially on a new motor. Make sure the oil isnt full of gas. Its dumping the fuel, has air (7lbs of boost), so is it not getting a good spark? Double check the gap on teh plugs, the ceramic didnt get cracked by accident did it? Otherwise id be looking for a sesor reading something wacky and commanding the computer to do something even wackier.

Are they seeing any knock retard? False knock maybe?

OC Corvette is an excellent shop. My car is there right now. Blown Blue Z06.

Im sure Sean will find the problem. He is more than competent.

Okay here is the deal.
At about 4800 rpm the injectors take a dive and lean the car out and they don't push it any further. Thankfully they don't push it! So the fuel is getting there but just dropping off. They can't figure why. The injectors are at 80% duty cycle and then drop to 45% I think is what they said. Everything else is fine, no KR.
Any ideas?
it is at about 403RWHP but it hasn't gone over 5000RPM because of the fuel issue.
See this is why I am glad it is here! They realise pushing it might break it and they don't unlike the last shop!

Okay here is the deal.
At about 4800 rpm the injectors take a dive and lean the car out and they don't push it any further. Thankfully they don't push it! So the fuel is getting there but just dropping off. They can't figure why. The injectors are at 80% duty cycle and then drop to 45% I think is what they said. Everything else is fine, no KR.
Any ideas?
it is at about 403RWHP but it hasn't gone over 5000RPM because of the fuel issue.
See this is why I am glad it is here! They realise pushing it might break it and they don't unlike the last shop!

Is the fuel pressure holding up?

Fuel pressure stays fine, duty cycle of the injectors drops off.
Pulled the #2 spark plug and it looks fine, a little black from running so rich but nothing bad. In the process of checking compression on that #2 to see what compression is.

ALSO the oil pressure dropped when it was coming down from the last pull? It dropped down to 0 I think they said, it was fine during the pull but dropped out coming down? Any ideas there?

ALSO the oil pressure dropped when it was coming down from the last pull? It dropped down to 0 I think they said, it was fine during the pull but dropped out coming down? Any ideas there?

This is probably way off but maybe you have a bad ground somewhere.

Don't those types of blowers pull in air at a squared rate? Pardon my inability to correctly articulate my question, hope someone gets it.

Basically what I'm asking is if at 5k RPM its pulling 7 PSI at 80 percent duty cycle, wont that indicate that the injectors arn't safely gonna supply full past that level? Since boost will increase as RPM increaes, wont it? I may be thinking of the wrong kind of blower here, too.

Please correct me if I'm wrong.

Maybe you have a bad injector driver in the pcm. Try swapping another pcm, upload the tune they are working with and see what happens. That the only thing I can think of that would cause you inj dc to fall off or possibly a loose or inadequate ground wire like mentioned above. I have seen where a loose grounding strap caused the ground strap to cook and burn it up making it useless

See if you can get a dyno graph with hp and tq along with afr over engine rpm not tire speed and post it up

If they are reading the duty cycle falling off from the ECM, there is nothing wrong with the fuel system or blower, the ECM simply isn't calling for more fuel. I would check the signal coming from the mass air meter. A bad connection or turbulence in the MAF could be sending a false reading to the ecm, which it will interpret to mean the motor has less air, needing less fuel. Are they using a wide band? If not, the fuel flow dropping like that is a sure fire way to burn up your new motor when its on boost.

Well I am going to take it home tomorrow. I will be checking all the ground wires, which to do that I am going to have find the ECU pin map or whatever it is called. Then I am going to try to find another ECU and switch that. I am going to drive the car for a few hundred miles in the mean time to see if I can get a better seat on the rings. So they have set the rev limiter to 4500 or something so it doesn't go near the unsafe limit on the engine. and I will not be racing it around. I just need it back because my husband is coming home and needs a car to drive to work for the week. After that it will be down a little bit longer to have the paint fixed and try to work out these other issues.
THanks for the help. I will keep you posted.

Just make sure you get the other ecm reflashed with the boosted tune before you try and drive on it

I wouldn't be doing shit until I figured out why the oil pressure was at zero. You aren't gonna put "a few hundred miles" on it like that.

Yeah no crap... Make sure that your oil pump isn't crapping out on you..

havent' bothered reading all the responses but the G trim is way too small for your combo. Run a T trim at the minimum if not a ysi, you can still use the aftercooler.

where are you located if you're in florida i could look at the setup. i'm pretty familiar with vortechs.

55# inj's at 80% duty cycle, and making <400HP??
I'd be REAL curious as to where all that fuel is going.. :bang:
FAST injs are rated at 55# @ 3 bars. If so, at 58psi, that's a TON of fuel at 80%!! :eek2:

those injectors on that size engine are too small. i bet she is making peak power at like 4-4500 rpm.

she'll probably need 72's.

what she needs to do is datalog the run and see what is going on. i'd get a grip on the oil pressure thing first that could be a loose wire

Okay here is the deal.
At about 4800 rpm the injectors take a dive and lean the car out and they don't push it any further. Thankfully they don't push it! So the fuel is getting there but just dropping off. They can't figure why. The injectors are at 80% duty cycle and then drop to 45% I think is what they said. Everything else is fine, no KR.
Any ideas?
it is at about 403RWHP but it hasn't gone over 5000RPM because of the fuel issue.
See this is why I am glad it is here! They realise pushing it might break it and they don't unlike the last shop!

Is your plug gap wider then say .030 or 0.035 ??? if so you are blowing out the plugs. This explaisn the lean spike( lean Missfire as read by the Wideband) and lack of HP. Gap the plugs down to 0.020 try again. Judging Get a Blower or turbo specific plug with an exposed eletrode. Sounds like your blowing out the spark plug. try seeing what that gets you.

Any luck yet? New info, or problems found?

First thing I would try is some sort of voltage booster to help fuel pumps/ignition at higher RPM's. I'm using the Casper Volt Booster...good luck and post up what you've found out.

Bump I am curious to see the fix on this one.