I’ll try make this as to point but detailed and short as possible!















6 months ago got fresh build started. Twin t4 gt35s on a 5.3 with basemap really rich. Twin 40mm precision wastegates. I had wastegates routed back into downpipes with no exhaust yet. Put car on dyno for a break in with rings or whatever and car made full pulls for 10psi-14psi. Super rich but not breaking up. After I found hotside leaks and sent car to get full dual 3.5” exhaust installed and fix hotside. Also I wanted to remove dump tube from going into downpipe and put to atmosphere because I had about 2-3psi creep after full boost.... this is all on spring pressure no controller.

last month I get car back from exhaust place. No dump tubes on car yet. So wastegates just facing downpipes open. The top nipple on TB flew out so I threaded and plugged that hole. Fixed a vacuum leak I had on intake. After that the car wouldn’t start without TB screw opened. I followed write up to open TB to 2% then reset sensors. It worked fine. No small stalling or garbage cold start. Put bunch of miles on car with 0 boosting. Car never broke up for a second and was pretty smooth.

4 days ago I leave my buddy’s house, clutch kicked first gear and boosted who knows what lol. Should’ve been the 14psi spring though. Anyways, I melted 3 plug wires cause they were resting on exhaust manifolds. Limped car home.

next day, fix plug wires and make new bracket for coil packs to face strut towers and not manifolds. Drive car and boost 1st then 2nd gear and I let off because boost was 15-16psi. No break up just over boost so I let off pedal and drove normal for alittle before going home.

2 days ago I take wastegates off car to put lighter springs in them. While they off I try to put air into nipple to see what pressure springs should be. I used my leak down tester as a regulator for pressure. It would need 20+ psi to open valve slightly! If I get the valve alittle pressure with my finger it would open up quicker than the 20+ psi. So I remove spring entirely and The valve without spring lid would move up and down easy and smooth. I put the springs back in and I can physically push the valve with 2 thumbs up and down. Not hard to do physically. However with air pressure it needed crazy amounts unless I gave alittle pressure on valve with my fingers. So I take those 12psi springs (same that gave me 14psi at 3800rpms on dyno) out Of wastegates and I put in the 8psi ones. These 8psi springs are really easy to push valve open and shut physically but with air pressure they will crack open around 15psi and don’t fully open without boat loads on air pressure. UNLESS my finger is putting alittle pressure on valve. I DO NOT feel any burrs on the valve stem and it moves smooth physically.
after that ordeal I install the 8psi spring to wastegates and put onto the car. I drive the car and it goes 8-10psi and breaks up bad so I let off gas pedal. So I ease into boost again, no break ups or roughness into boost or before boost. Only at that peak pressure. I ease into boost and sure enough around 5-6psi it just breaks up.

i go home and install my new spark plugs and brand new coil wires. Thinking something broke from other day. Drive car again and it repeats same thing. I do not think it’s a spark blow out or fuel issue. Wideband is 10.0 and it’s been on dyno with same basemap without breaking up with higher fuel pressure than now. Plugs are brand new tr7 and last tr6 plugs had no issues. It’s only after I played with wastegates. The car as a whole sputters under max boost not like 2 cyl misfiring. Also there’s noise under the hood so I’m really thinking the waste gates are slamming shut after starting open at 5psi. The boost gauge needle jumps 5-6psi whole time under full boost and car sputters. Keep in mind that all this seat time is super quick. Car is in 2nd gear and gets to full boost immediately. I’m not holding pedal down once sputters either. Feels like death lol.

pressure lines are hooked to outlets on turbo and hooked to wastegate nipple closest to valve and the top nipple is vented. Idk where to go from here. Wanted car go to tune Monday but can’t with it not holding 1 full pull. I’m going try put the larger springs into wastegate and see if sputters moves to the 14psi or stays at 5psi. These waste gates seemed to work fine on dyno months back just alittle creep. Now it’s like they starting open and it’s being slammed shut tons of times in a second.

 

so in trying to get a video to hear the noise it makes, I had to stay on gas pedal... think it’s just waste gate air pushed into frame of car. I don’t have a dump tube routes yet. The air coming out of wastegates vibrates entire car man. You can feel them it in whole car when it’s open. It’s like a rasp. Idk how to explain it. You can hear it in one of videos that start higher rpm.

this first time boosting car on road for longer than second without tire spin. Funny part is I had creep before with gates going into my exhaust and now I put 8 psi springs into it and it boost at 5-6psi. So I add the 4 psi springs to the 8 and I’m getting about 8 psi. When I was installing the springs before I didn’t realize there is notches on the base and cap of wastegate, so it must’ve been sitting crooked and wouldn’t open normally. So 12lb spring would be 15+ now it’s sitting right and my 8+4 springs give me 8 lol.

 

10.0 afr is stupid rich. Put a borescope in there and see if you did't lift a few ringlands. If not, lean it out and see if you're still having issues.

I'm not a fan of those spark plug covers. They trap heat inside and end up still burning up the wire.

 

it’s a basemap so I can’t touch it. I don’t tune. I’ve lowered the fuel pressure to 38 and I get a 15.6 ish a/f cruising but anytime on gas it seems always go to 10.0 lol. As long as it mechanically isn’t breaking up then I’m sending him car Monday anyways for tune. As is with fuel pressure drop I did , it affect idle and alittle dip in neutral.

 

So my tuner is busy for few weeks so I put car on dyno for 2 pulls last night to confirm my sputter I was feeling is not my setup but something fixable in the tune. I have a cruise next weekend for my best friend who died years back. So I wanted to make sure I can drive car next weekend without issues... here is results. The feeling I’ve had is just a bunch of gas.

This first run was locked regulator at 48psi, I let off cause started to lean out at 12.3 air fuel. This was not how it’s been driving.


This next pic is how cars been driving. 48psi regulator with boost line added.


Never been so anxious waiting for something. Need it tuned so bad.

 

I would stop going WOT on a basemap. Basemaps are made to get the car from point a to point b or to allow low rpm break-in, not to get into boost and flog it.

 

Stop flogging the car on a base tune.

 

I’m not boosting on it. Just normal driving till tune.

 

Your first post is littered with different boost level info.

 

that was before I realized where it was at other night... last time I put it on dyno the swap was brand new and had no exhaust etc. now car is tune ready but I put on dyno to be 100% an issue I was chasing was tune related after playing with melted plug wires and wastegate issues.

now I know where I am with tune and I know the swap isn’t at fault. No reason to bring car for tune if I have other issues.

 

I’m not going to pretend I haven’t done some 2nd gear pulls or the 2 runs on dyno. Knowing what I know now, it prob was mistake but that’s all done with and now I’m scheduled and super close to tuning considering car been project for a year.

 

Most widebands stop at 10.0 so you have no idea how rich you were. Breaking up in boost with an AFR that rich isn't surprising.

 

Just add boost until it isn't rich anymore

 

yesssssss!

 

Have someone doing a tune for it tmr without the m1. So just a regular 93 pump tune. If all goes well, I can do 550-600rwhp on the gen3 rods for the summer and build a 5.3 block for later on.

 

The street loads it differently than a dyno. It puts the load cells in a different spot on the fuel map. When you had the stiffer springs you were at more boost, and likely the tune wasn't as rich at that boost level, so it didn't break up. So when you put lighter springs in it lowered the boost to a point on the map that was much to rich and broke up. When you went to the dyno again, it still wasn't in the same load cell area as it would be on the street, so it's not going to act the same on the road once it comes off the dyno. If the AFR is ever reading 10.0, just stop and have the car tuned. No reason to flog on it, it won't get better.